Repowering,Part 2

By Don Casey

Article taken from Good Old Boat magazine: Volume 3, Number 1, January/February 2000.

Installing a new engine Part 2: Getting it to fit

In the November 1999 issue, well-known marine author Don Casey described
how to remove the old engine from your good old boat. Now it’s time for
the final exciting step …

Leveled cross pieces just touch the centering string and help transfer the shaft centerline to the stringers.

Even though engine brochures generally provide all the measurements you
need, it’s hard to reconcile them in three dimensions while the old engine
is still in place. That’s why I delayed ordering the new engine until the
old one was out and I could see exactly how a new one would fit.

To do this most effectively, I used a half sheet of foam insulation board,
a razor knife, and a roll of duct tape to construct a rudimentary three-dimensional
model. This took about 20 minutes, and it let me see exactly how much space
there would be between the flywheel housing and the hull, between the top
of the engine and the cockpit sole, between the alternator and a scupper
hose.

I was able to move the foam “engine” easily to the limit of the stringers
to evaluate clearance and access. An unplanned benefit of the foam engine
was that it also helped me visualize the configuration of the new exhaust
system and the routing of fuel lines and control cables. It also revealed,
to my consternation, that the old rails weren’t parallel.

Now, confident that the real engine would hold no surprises, I gave my dealer
the green light. A truck showed up at the yard exactly a week later with
the new engine.

Fuel-tank issues

Don’t overlook the fuel tank. If the existing tank is galvanized – not uncommon
for gasoline – you must replace it. A galvanized tank will flake particles
of zinc into diesel fuel, blocking filters and injectors.

If the tank isn’t galvanized, but is captured by the engine, replacing it
now might be a case of “a stitch in time.” Our fuel tank happened to be
made of Monel metal, but I still wanted to pressure test it for leaks. This
became easier when I discovered that a 1 1/4-inch threaded PVC plug was
a perfect fit for the deck fill. I drilled a hole in the plug and installed
a standard tire valve. I clamped short lengths of fuel hose to the outlet
and vent fittings, then squeezed the hose closed with Vise-Grip pliers.
A half-dozen strokes with a bicycle pump put the tank under light pressure,
which I checked with a gauge. Never (I repeat, never) put more than about
3 pounds of pressure in the tank. When the tank was still under pressure
the following day, I was satisfied that it was sound.

The next issue was 30 years of sludge. Having the tank professionally cleaned
might have been a better option, but good access lured me into cleaning
it myself. I drained the tank, then “scrubbed” the interior with rags stapled
to a dowel. It turned out to be a tedious process, but eventually the rags
came out clean.

If you convert a gasoline tank to diesel, you’ll need an additional fitting
for the return of excess fuel. The neatest way to accomplish this is to
drill a hole in the vent connection (remove it first, of course) and braze
a hose barb over this hole. Return fuel is hot and should not go directly
back to the engine, so do not put the return line barb on the pick-up fitting.

Finding the prop line

With the tank checked and cleaned, I turned my attention to the engine bed.
The existing stringers were too tall, but it was essential to get them to
the right height relative to the propshaft. I did this by stretching a string
through the stern tube and across the engine space. Outside, I fastened
the string to the rudder. Inside, I tied a heavy weight to the string and
hung it over a length of cleat stock with a notch in the top surface to
catch the string. This was clamped to either side of the engine hatch. By
moving the notched board up and down, and from side to side (and with smaller
adjustments of the outside attachment point) the string can be positioned
in the center of the stern tube at both ends. This is the centerline of
the propshaft, and it must also be the centerline of the transmission’s
output shaft.

The engine and shaft must be in precise alignment.

More to the immediate point, because the distance below the driveshaft centerline
is the same for all four mounts on the Yanmar, this string also marks the
correct incline for the engine stringers. To project this line onto the
stringers, I cut two lengths of square stock to an interference fit between
the stringers, wedged them in place just touching the string, then leveled
them side to side with a bubble level. (I had already checked to make sure
the boat had been blocked up level.) Tracing their top surfaces onto the
stringers gave me the necessary two points to draw a line at the same height
and incline as the shaft centerline.

But the bottoms of the mounts aren’t at the same height as the shaft. On
this particular engine, Yanmar specifies a position of from 0.87 to 1.42
inches below the shaft centerline. Reasoning that the mounts would compress
with time, I chose the end of the range that gave me the highest stringers.
Allowing a few extra thousandths for the planned overlay of glass sheathing,
I drew a second line on the stringers 0.95 inch below the first. Using a
circular saw and a clamped board as a guide, I cut each stringer on this
second line. Because the rise of the hull interfered with the saw at the
aft end, some handwork was required to complete the cuts.

The old rails were 1 1/2 inches too far apart in the front and nearly 3
inches too far apart in the back. I addressed this by sistering 1 1/2-inch
thick white oak to the inside of the rails. Ideally, these pieces should
have been wedge-shaped, but I couldn’t see any easy way to accomplish that,
so I simply chamfered the top after installation to provide adequate clearance
for the engine. I also added a couple of wooden gussets to the outside of
the stringers, more to dampen vibration than to add strength. A couple of
layers of fiberglass cloth over the rails and generously lapped onto the
well-ground hull, completed the engine bed.

No heavy lifting

A simple plywood jig eliminates the need to move the heavy engine onto the
bed until you are ready to bolt it in place. Make the jig from a flat piece
of 1/2-inch plywood the length and width of the engine. With one end representing
the mating surface of the drive flange, use a square to mark a centerline
on the board. Measure from the flange end and the centerline to locate exactly
the four holes for the flexible mounts, and drill them to the same diameter
as the matching holes in the engine brackets.

Attach a perpendicular piece of plywood on the centerline at either end
of the jig. These should be slightly longer than the distance between the
bottom surface of the mount brackets on the engine and the centerline of
the drive shaft – a dimension provided on the engine drawing. Mark this
distance on centerlines extended (with a square) from the jig centerline
and drill 1/4-inch holes at the marks. Saw into these two holes so you can
slip them over the centering string.

Rerig the centering string, making sure it is in the center of the stern
tube at both ends. Bolt the flexible mounts to the jig and set it on the
engine bed, guiding the centering string through the saw cuts into the 1/4-inch
alignment holes. Slide the jig fore and aft and side to side to position
the mounts where you want them, then turn the adjusting nuts – the ones
underneath – to raise or lower the jig until the centering string is in
the center of both holes. Be sure you keep the jig level side to side and
the mounts parallel to the centerline. Trace the mount holes onto the stringers,
then remove the mounts from the jig and – without turning the adjusting
nut – bolt them to the corresponding mount bracket on the engine. A word
of caution here: even though the mounts look identical, there may be a difference
in the elasticity between front and rear, so make sure you position them
correctly on the jig to start with.

Drill the stringers for the lag screws that will hold the mounts in place,
and you are ready to install the engine.

In with the new

Plywood jig centered on the centering string.

When the new engine arrived, the masts were still out of the boat, so I
had the yard lift the engine with their boom truck and lower it through
the companionway into the main cabin. Getting it under the cockpit was the
reverse of dragging the old engine out, except that I couldn’t bear the
thought of scraping that shiny paint off the bottom of the oil pan. I tacked
a cleat stock stop across the end of a small rectangle of plywood and set
the engine onto this “sled” for its short ride aft.

When the engine was in place, I installed the lag screws, snugging them
down, then backing them off half a turn to allow some later lateral adjustment
of the engine.

Prop and shaft

Prop configuration – diameter, pitch, number of blades, blade area, and
so forth – is another subject altogether, but you do need to know the maximum
prop diameter to determine the appropriate shaft diameter. The formula for
propeller diameter is (632.7 x shaft horsepower0.2) / shaft RPM0.6, but
as a practical matter, prop diameter on a sailboat is more often determined
by clearance or acceptable drag. For example, the Yanmar I had selected,
with a 2.61 reduction gear, is best mated to a 16-inch prop, but allowing
the necessary tip clearance of around 15 percent of prop diameter, hull
configuration limited me to a 15-inch prop. (I could have selected a lower
reduction gear, but I preferred the slower shaft speeds.)

The rule of thumb for shaft diameter is one fourteenth of prop diameter.
That is 1.07 inches for a 15-inch prop, which squares well with Yanmar’s
recommendation of 1.1-inch shaft diameter for this engine. This assumes
bronze or stainless steel, but you can safely reduce the diameter of a Monel
or Aquamet shaft by 20 percent. Our existing Monel shaft could have done
the job, but it was more important to me to have the engine as far forward
as possible.

To determine the length of the new shaft, I temporarily bolted the shaft
half of the new coupling to the drive flange. Inserting the old shaft into
the stern tube to the mark I had made before extracting it, I was able to
measure from the interior face of the flange to the end of the old shaft.
I needed a shaft exactly 10 inches longer than the old one. But to isolate
the prop electrically, I had decided to insert a flexible coupling in the
drive train, which would move the coupling aft 1 inch.

The 7/8-inch diameter of the old shaft was marginal, so I decided to make
the new one 1 inch in diameter, if I could do it without modifying the stern
tube. A quick check of catalogs revealed that I could buy a 1-inch Cutless
bearing with the same shell diameter as the 7/8-inch bearing. The prop shop
had a 1-inch stuffing box that would fit my stern tube, priced at less than
$50, complete with a new hose.

I ordered a 1-inch Aquamet 19 shaft, 9 inches longer than the old one, and
had the prop shop fit and face the coupling. They also reconditioned the
old prop and rebored it for the larger shaft. Prop shops often designate
shaft length to the small end of the taper, so be careful that you tell
them exactly how you arrived at your measurements. A drawing is a good idea.

With all the parts in hand, I installed the new Cutless bearing, quad-clamped
the new stuffing box in place, inserted the new shaft, and installed the
new flange.

The crowd roared

With the shaft flange just shy of the drive flange, I moved the shaft up
and down to find the center position. Supporting it there, I checked for
misalignment with a straightedge. None. I slid the shaft forward and the
coupling mated with a satisfying thunk. The crowd roared, but it was the
centerline string and the plywood jig that deserved all the glory.

I checked the space between the two halves of the coupling with a feeler
gauge. The maximum gap was about 0.012. Not good enough.

The engine and shaft must be in precise alignment.

Yanmar specifies a maximum face runout of 0.008, so I tapped the forward
mounts slightly to starboard and gave the adjusting nuts on those same mounts
about a half turn. The maximum gap dropped to 0.005. Now it was good enough.
The boat would likely change shape slightly when it went back in the water,
and I would recheck the alignment then.

Finally, I separated the coupling and reassembled it with a flexible doughnut
(Drivesaver) between the flanges.

Dripless packing

Because I find simplicity nearly always superior at sea, I decided against
a mechanical shaft seal. But I was interested in trying dripless packing
in hopes of minimizing how many times I would have to tighten the stuffing
box.

Dripless packing turned out to be easy to install, captured on either end
with rings of standard Teflon packing. The only drawback so far is the substantial
cost.

Wiring and plumbing

Using a centering string to determine the propshaft centerline.

It would have been easier to install the fuel and seawater filters and the
coolant subtank while the engine compartment was empty, but I wasn’t sure
of their exact locations until the engine was in place. The engine came
with the subtank and a Racor fuel filter, and at the suggestion of Mike
Muessel, president of Oldport Marine Services in Newport, R.I., who served
as my technical advisor, I selected a Vetus above-the-waterline raw water
filter.

The subtank came with its own hose, but the barb at the engine fill faced
the wrong way. To keep the hose run as short and straight as possible, I
unbolted the filler neck and turned it around, taking care not to damage
the gasket.

The water connection should have been a snap – a 3/4-inch hose from the
through-hull fitting to the filter, and a second hose from the filter to
the engine. Inexplicably, however, the barb on the engine turned out to
be 5/8 inch, so a hose adapter was required. Always make raw water connections
with reinforced (suction) hose so it will not collapse if the through-hull
or the filter become partially blocked. Double clamp all below-the-waterline
connections.

Fuel hose (types A1 or A2) makes fuel connections as easy as water connections.
The line from the tank to the engine is broken twice, once for the shut-off
valve and again for the primary filter. The return line leads directly from
the engine to the tank.

The most difficult connection is probably the exhaust. Waterlift mufflers
have become nearly universal, but they must be installed properly or they
have the potential to flood the engine. Guidance is widely available.

I elected to install a Vetus waterlift muffler, but because the bilge configuration
prevented mounting it well below the mixing elbow, I used a galvanized nipple
and a threaded coupling to raise the elbow. This provides increased resistance
to backflooding and has the added benefit of raising the water injection
connection above the waterline, eliminating the risk of water siphoning
into the engine through the raw-water pump. A gooseneck muffler at the transom
that takes the exhaust line right up to the underside of the deck before
exiting the transom somewhat lower, should prevent following seas from forcing
water back into the engine.

Single-lever control

Out in the cockpit, I installed a new single-lever engine control – the
old engine had a separate shift and pull-up throttle. I used an old cable
as a “scout” to determine the route and length of the new cables.

The cockpit was also the logical location of the new instrument panel, although
the installation instructions cautioned against exposing it to the weather.
Recessed enclosures are available, but in our cockpit there was no place
to install one. The alternative was a custom teak frame with a gasketed
acrylic cover.

I was disappointed to discover that the only instrument on the “instrument
panel” was a tachometer. No oil gauge, no water-temperature gauge, no ammeter,
and no engine-hours meter. Lights and alarms are certainly better at announcing
a problem, but I find gauges very useful in heading off the kinds of problems
that eventually sound an alarm. Gauges are on my shopping list.

The good news is, after you mount the panel, wiring it up is dead simple:
connect one end of the furnished harness to the plugs hanging from the back
of the panel, the other end to the plugs on the engine. That is it.

The only other electrical connections are the battery cable connections
to the starter. If you are replacing a gasoline engine, be cognizant that
the starting loads will be much higher for the diesel. Your existing battery
cables are probably too small. How big they need to be depends on the current
draw of the starter motor and the round-trip length of the cables. The appropriate
cable size for our installation was 2/0. Don’t scrimp here. This will make
the difference between starting and being dead in the water when your batteries
are low.

Running the engine

Cutting down the engine stringers to the correct height

Fill the engine and transmission with the specified oils. Make up a 50/50
mix of antifreeze, and fill the header tank and the subtank. Fill the fuel
tank with fresh fuel and bleed the fuel system according to the engine-manual
instructions. The only remaining requirement is a flow of cooling water.

In the yard, I disconnected the pick-up hose from its through-hull and stuffed
it through a nearby 1 1/2 inch through-hull fitting for a (disconnected)
cockpit scupper. Outside the boat, I supported a bucket against the hull
and over the fitting, with the pick-up hose extending down into the bucket.
A running garden hose secured to the bucket kept it full and overflowing.
I also used the hose momentarily to prime the pickup line. If you don’t
have a convenient through-hull, you can wedge the bucket next to the engine
and let the bilge pump take care of the overflow.

To get oil to the engine before starting, it is always advisable to spin
it with the starter for about 5 seconds while continuously pulling the kill
knob to prevent starting. After this precaution, I turned on the key, hit
the starter, and the engine fired, clattered for a moment, then settled
into a satisfying purr. A look over the side confirmed that the cooling
water was flowing through the engine and out of the exhaust. In fact, I
was surprised at how much water the pump drew. When I increased the engine
speed, the faucet had to be wide open for the garden hose to maintain a
full bucket. Don’t let the water level drop below the pick-up hose or you
will burn up the pump impeller.

Once in the water, you will need to check engine/shaft alignment one more
time. Take the time to tweak it in as close to perfect as you can get it.

After a couple of engine hours, open the throttle all the way to see if
your prop selection was correct. Ideally, the engine should just reach the
maximum specified RPM. If it runs faster, you need more pitch. If you can’t
reach maximum revolutions, less pitch is indicated. However, being slightly
overpropped (too much pitch) does put more power into the water at cruising
RPM, not altogether a bad thing.

Worth the effort?

Lower levels of irritation and worry are intrinsic benefits of a new engine,
but installing it yourself offers other bonuses. There is, of course, the
pocketful of money you will have saved. Doing it yourself lets you determine
the level of workmanship. You can also expect a satisfying sense of accomplishment.
But perhaps the biggest advantage is an immediate intimacy with the new
engine. The knowledge of how all the components work together and what they
need from you to keep working provides a matchless basis for a long and
happy symbiosis.

Don
Casey abandoned a career in banking in 1983 to devote more time to cruising
and writing. His work combining these two passions has appeared in many
popular sailing magazines. He and his wife, Olga, cruise aboard their 30-year
old Allied Seawind. They like to point out that they’ve done all the work
themselves with no adult supervision. Don co-authored Sensible Cruising:
The Thoreau Approach and became the authority on boat fix-it projects
with his book, This Old Boat. He is the author of a series of how-to
books in the International Marine Sailboat Library Series. Don has
also written Dragged Aboard – A Cruising Guide for the Reluctant Mate.

Repowering, Part 1

By Don Casey

Article taken from Good Old Boat magazine: Volume 2, Number 6, November/December 1999.

This is first of a two-part series by well-known boating author Don Casey.
Here he tells exactly how he extracted an Albin diesel from his good old
boat.

What you need to know before removing the old engine

The engine and shaft must be in precise alignment. This is
the only hard, fast rule for installing a new engine in an old boat. Everything
else you make up as you go along.
I pass this on to you with the authority of having just repowered our own
good old boat. I am also pleased to tell you the process turned out to offer
fewer opportunities for disaster than I had imagined.

Why repower?

Until recently, repowering a sailboat nearly always meant replacing a gasoline-fueled
engine with a diesel. Today, the engine coming out is nearly as likely to
be a diesel. Sometimes the owner simply wants more power, but more often,
the replacement has to do with either the cost or availability of parts
for the old engine. My own experience is a case in point.

Our old boat, an Allied Seawind, came from the factory with a 20-horsepower
Albin AD-2, a Swedish diesel as dependable as a St. Bernard and as rugged
as stone. But after 30 years of service, the time for a major overhaul was
at hand.

In common with a lot of other European diesels of the same era, Albin has
almost disappeared in America. There was no place that I was willing to
take the engine for a rebuild. And even if I could get the job done in a
monastery workshop, then what? Already I had seen water-pump impellers out
of stock for nearly a year. If I couldn’t get the most common replacement
part now, what were the odds of getting a rocker arm in Trinidad five years
from now? All things considered, a new engine promised to be the better
choice.

How much power?

The first step in selecting an engine is determining horsepower requirements. Skene’s Elements of Yacht Design, by Francis Kiney, and Dave Gerr’s Propeller Handbook both contain formulas that allow you to estimate
power requirements based on displacement and waterline length, but it is
important not to overvalue such calculations. They only tell you the theoretical
horsepower needed to push your boat through smooth water. Punching through
waves requires additional power. So does motoring against a breeze. Or overcoming
a foul bottom. If the displacement amount doesn’t include the weight of
equipment, supplies, and crew, the calculations understate power requirements.
And they assume a propeller with more surface area than you may want to
drag around under sail.

The truth is these formulas are a migraine you don’t need. They are going
to tell you that you need about 2 horsepower per 1,000 pounds of displacement. (Editor’s note: We used Dave Gerr’s formulas for calculating our own power
requirements when repowering. We found them to be useful and comforting.
In the end, we selected an engine with about 2 horsepower per 1,000 pounds
of all-up cruising weight.) How can I know that in advance? Because
the game is fixed. The only variable is the speed-length ratio, and virtually
all displacement sailboats have a theoretical speed-length ratio of about
1.3.

Since you are repowering, you can also deduce your power requirement empirically.
How satisfactory was the old engine? If, for example, the old engine was
anemic against a breeze, you need a bit more horsepower this time. On the
other hand, if you never saw the tachometer above 2,000 rpm, a look at the
engine’s output curve (example on next page) will show how much horsepower
you have been getting along with.

In our case, the 2-horsepower rule yielded 24 horsepower, but I already
knew that 20 would push us along smartly in smooth water. A few times, extra
ponies would have been reassuring, but the rest of the time a bigger engine
would be loafing. Because diesel engines do better under load, I felt reluctant
to add power, but the particular engine I wanted was available in either
a 16-horsepower, 2-cylinder version, or as a 24-horsepower, 3 cylinder. (Note: These are continuous horsepower ratings. Advertised ratings often
are intermittent horsepower – meaning you can run the engine at that load
for no more than one hour. Intermittent horsepower is typically 10 to 15
percent higher than continuous horsepower.)

Ultimately, I settled on the 24-horsepower motor, and my somewhat convoluted
logic might be helpful. The primary issue for me was idling, not powering.
For years, we had run the old engine at anchor for up to two hours a day
to keep the batteries charged and the holding plates frozen. A smaller engine
would better tolerate this light load, and had we intended to continue accumulating
most of our engine hours at anchor, I would have installed the smaller engine.

However, we have abandoned the main engine for refrigeration and primary
charging, using it only for propulsion. With no compressor belted off the
new engine, 16 horsepower still would likely have been adequate-just. However,
the one-time-only opportunity of banking 50 percent more power for an additional
investment of about a grand carried the day.

It is common practice
to factor in additional horsepower for engine-driven accessories such as
a high-output alternator, a refrigeration compressor, or a watermaker. This,
I think, is unnecessary and probably even undesirable, except for engines
under 10 horsepower. At less than full throttle, the propeller absorbs considerably
less horsepower than the engine can produce, so plenty of extra power is
available. You can determine how much from the spread between the engine
power curve and the one for the propeller. Or, if your old engine is a diesel,
multiply your average fuel consumption (in gallons per hour) times 16 to
arrive at the average load on the engine in horsepower. (We can make this
calculation because 1 gallon of diesel fuel will produce around 16 horsepower
for 1 hour.) If, for example, your usual consumption is 0.5 gallon per hour,
you are using only about 8 horsepower. The difference between this number
and the continuous horsepower rating of the engine is unused capacity. It
just makes sense to make use of this excess before adding dedicated capacity.

Loading the engine more heavily more of the time also extends its life.
On those rare occasions when you want all the engine’s power available at
the prop, it is a simple matter to turn off the auxiliary loads. For those
unswayed by this logic, in the absence of specific power requirements for
these auxiliary loads, a 2-horsepower allowance for each won’t be far off.

Which engine?

After you arrive at the target horsepower, the next choice is whose engine
to buy. Here the primary issue may be fit, but probably not size. Today’s
engines are nearly all smaller than older engines of similar or slightly
less horsepower. The main fit issue is the location of the output flange.

The engine and shaft must be in precise alignment.

With battens, a tape measure, and a few body contortions, you should be
able to determine the height of the shaft relative to the engine bed. While
you are bent like that, also measure the length, individual width, and center-to-center
width of the bed stringers. Wait, don’t straighten out yet. How far below
the stringers can the engine extend? How much room do you have above the
stringers? Now get all these dimensions on paper, and you are ready to qualify
or rule out any engine you may be considering.

Access is another concern. If you can only get to one side of the engine,
you want filters, pumps, and dipsticks on that side. Will you be able to
service the starter without removing the engine? Will there be room above
the valve cover for an upturned oil container?

If your budget has you contemplating a seawater-cooled engine, snap out
of it. Unless you use the engine only in fresh water, seawater cooling is
a bad idea. Scale will form in the cooling passages, eventually leading
to overheating. Running the engine at lower temperatures to retard scaling
only postpones the inevitable, and it reduces the engine’s efficiency. Freshwater
cooling has become the norm for good reason.

Because a diesel doesn’t require electricity to run, hand-starting is an
attractive feature. Dead battery? Get out the crank. It’s a nice fantasy,
but the reality is that sailboat installations rarely allow adequate room
to spin the crank safely. Make sure yours does before fretting over the
absence of this feature. An extra battery or a small generator in the lazarette
accomplishes the same thing without the risk of broken bones.

The fact that I was replacing an engine perfectly capable of delivering
another 30 years of reliable service, if parts for it were still available
and/or affordable, colored my decision from the start. I wanted an engine
that had already been installed by the thousands, by the tens of thousands,
reasoning that this was our best assurance of wide and long parts availability.
For our size boat, that engine was the Yanmar GM series.

Reliability was equally important, so I made inquiries. No owner I talked
with had a single negative thing to say about the engine. This should not
be construed to suggest that Yanmar engines are more reliable than competitive
brands, but it did give me assurance that they are no less reliable. Once
I was satisfied that the engine would fit, my choice was pretty well set.

Price, by the way, played no part in my choice. I reasoned that $1,000 difference
one way or the other, amortized over 30 years, works out to $33 a year.
That was insufficient for me to make any compromises. That did not, however,
keep me from negotiating the best price I could on the engine I wanted.

Buy the book

With the project still months down the road, there was no need to make a
firm commitment, but I was sure enough about the Yanmar that I decided to
ask about the availability of an installation manual.

Early on I had the good fortune of meeting Mike Muessel, president of Oldport
Marine Services in Newport, R.I. Taking unfair advantage of Mike’s enthusiastic
nature, I had committed him to become my technical advisor. (Both my engine
installation and this article have benefited greatly from Mike’s wise and
willing advice.) So I called Mike to inquire about getting an installation
manual in advance.

“Good plan,” Mike said. “And Yanmar’s is a good one.”

That turned out to be an understatement. The well-illustrated step-by-step
instructions were not only clear but reassuring. In addition, the 250-page
manual was a treasure-trove of helpful information, providing specific shaft
and prop recommendations, detailed engine specifications, and complete wiring
diagrams. Only twice during the project did this manual fail to answer every
question that popped into my buzzing brain. These were resolved with quick
email messages to Mike.

Whatever engine you select, buy the installation manual in advance; then,
with a yellow highlighter in hand, read it cover to cover. It will save
you the discomfort of uncertainty and maybe the misery of error.

Repowering afloat

It is quite possible to repower at the dock and, having the “ground” more
or less at deck level, makes it relatively easy to transfer the engines
to and from shore using the boat’s blocks, winches, and lines. Wrap the
boom directly above the companionway with a carpet scrap or beach towel,
and attach both the main halyard and the topping lift to a strop around
the boom at this location. Put both masthead lines under tension to support
the boom.

A chain hoist, or, with care, a multipart tackle (the main sheet) rigged
beneath the boom to the strop lets you lift the engine out of the cabin
and swing it into the cockpit or onto the cabintop. If you are using a tackle,
take the tail through a turning block to a winch. When the engine is on
deck, reposition the strop farther aft, and you should be able to use the
boom to swing the engine ashore onto a waiting dolly. Reverse the process
to get the new engine aboard.

Dockside repowering has less appeal when you have to remove the prop shaft.
This generally involves a diver extracting the shaft while a helper inside
slips a dowel or capped pipe into the stuffing box to plug the hole. This
can work as long as the new shaft is the same diameter as the old one, but
ifyou are adding horsepower, you may need a larger shaft diameter. That
means a new Cutless bearing and a new stuffing box, changes you don’t want
to make in the water.

I think there are significant advantages to having the boat out of the water
when repowering, regardless. Why?

The engine and shaft must be in precise alignment.

The process of aligning the engine is easier and infinitely more accurate
if you can use a centering line that passes through the stern tube. I am
going to explain this technique in detail, but it virtually assures a near-perfect
alignment right out of the box, saving hours of tedious adjustment.

A second reason to have the boat out of the water is to thwart human nature.
Engineering advances have resulted in shorter transmissions, so the weight
of the engine moves aft if you bolt it to the existing shaft. It is almost
always better to move the weight toward the center of the boat by positioning
the engine as far forward as possible, but this requires a new, longer shaft.
A larger-diameter shaft may also be indicated if the new engine is more
powerful than the old one. Having the boat in the water makes it more likely
that you will resist shaft replacement.

Even if the new engine mates perfectly with the old shaft, you still should
pull the shaft and inspect it for wear and corrosion. And while the shaft
is out anyway, it’s a good time to replace the Cutless bearing and repack
the stuffing box. You may also want to replace the hose that connects the
stuffing box to the stern tube. You won’t do any of these if the boat is
in the water.

Removing the shaft

I decided to do the job high and dry in the boatyard. Step One was to extract
the shaft. The prop had to come off first, so I borrowed a puller from the
yard. Never try to flail the prop off with a hammer, but a few love taps
on the center of the tensioned puller where it is pushing against the shaft
can be effective at breaking the prop free from the taper. I put an indelible
mark around the shaft where it exited the hull so I would be able to reposition
it later.

Inside the boat, I backed off the adjustment nut on the stuffing box so
the shaft would slide more easily. I also put another positioning mark on
the shaft, this one where it disappeared into the coupling. To prevent the
shaft key or anything else from dropping into the bilge, I spread a towel
beneath the coupling. Then I freed the shaft from the coupling. There is
a trick to this that, barring complications from corrosion, makes it a snap.

Loosen the clamp bolts or remove the setscrews and/or tap out the pin holding
the shaft in the coupling. You can try to slide the shaft out of the coupling,
but chances are it won’t budge. Mark both flanges so you can reassemble
them with the same orientation, then unbolt the coupling and take it apart,
sliding the shaft aft. Tape a strong spacer – a nut or a bolt – to the center
of the transmission flange, then reassemble the coupling and tighten the
bolts evenly. As the coupling bolts pull the shaft flange forward, the spacer
prevents the shaft from coming with it, thus pressing the shaft out of the
flange. Replace each spacer with a longer one – I eventually used sockets
– until the shaft drops out of the coupling.

With the shaft free, I slid it out of the boat and set it aside for later.
I also released the clamps around the stuffing box hose and twisted the
hose free of the stern tube.

Freeing the engine

The next step is to disconnect the old engine from its web of attached cables,
wires, and hoses. To avoid unwanted drama, start by unclamping the positive
battery cable(s) and removing it (them) from the battery post(s).

I disconnected the exhaust hose next, to gain better access. Since I wanted
the engine space to be totally empty for cleaning and painting, I also unclamped
the exhaust system from the hull fitting and removed it in its entirety.

The only water connection was a hose to the raw water pump. On the other
end of that hose was a screen filter with a glass housing, long on my list
for replacement. I removed the filter, unclamped the thru-hull connection,
and tossed the whole mess. Moving on to the fuel connection, I disconnected
it first from the tank so it wouldn’t set up a siphon. For the same reason,
I also disconnected the output side of the primary filter, using an old
towel to catch the inevitable dribble from the line. Only then did I disconnect
the feed to the engine. Using old fuel lines struck me as a bad way to save
20 bucks, so I dumped them. Yanmar promised a new Racor primary filter,
so I removed the old cartridge-style Fram, drained it into a plastic jug,
and gave the housing away. By the way, your preparation for repowering will
have to include locating an appropriate disposal site for fuel and oil.

Control cables were next. The old controls were not compatible with the
new engine, so as I disconnected each from the engine. I also detached it
from the boat, removing all associated clamps, supports, and mechanisms.
That left me with a few abandoned holes in the cockpit, which I closed with
fiberglass patches.

The old engine had an amazing number of wires connected to it – starter
and alternator connections, engine condition sensors, grounding wires, and
a few unidentified interlopers. At first, I labeled each as I disconnected
it, but I quickly came to my senses. The Yanmar installation manual showed
a plug-together harness connecting the new engine to its accompanying instrument
panel. The only existing wires that would be reconnected to the new engine
were the battery cables. So out came the wire cutter, and I clipped the
engine free of its wires in a matter of minutes. As it turned out, they
all lead, one way or another, to the old instrument panel or ignition switch,
and when I removed those, the engine space ended up empty of all wiring.

One word of caution: If you are using a smart regulator or have add-on meters,
you will need to identify, label, and save the hook-ups for those items.

Out with the old

When I extracted the lag screws fastening the engine mounts to the bed stringers,
the engine was free. Unfortunately, I still had to get its 500-pound bulk
from under the cockpit sole out into the main cabin, where it could be lifted
out of the boat.

Before I started moving the engine, I emptied the oil from the engine and
the transmission, and I drained out the coolant. I expected that I would
need to turn the engine on end to pass it through the companionway, and
I was hoping to avoid a messy spill. The alternator also had to come off
for the engine to fit through the engine hatch.

Next, I commandeered a 10-foot length of 2 x 12 the yard had lying around
for scaffolding. I slid it between the engine rails and pushed it back until
the aft end rode up on the hull as far as it would go. Lifting the board
against the bottom of the engine, I used a small bottle jack to raise the
forward end just enough to lift the mounts. With the board securely blocked
at this attitude, it was a simple matter to drag the engine out into the
main cabin with a come-along, taking care to keep the engine centered on
the board.

When the crane came to unstep the masts (I was also rerigging), the accommodating
operator also lifted the engine up through the companionway. The removal
part of the job was done.

(Next article: Insiders’ tricks for installing the new engine, shaft,
and propeller – how to avoid a hernia and many other setbacks on the way
to that magic moment when you turn the key, hit the starter, and fire up
for the first time.)

Don
Casey abandoned a career in banking in 1983 to devote more time to cruising
and writing. His work combining these two passions has appeared in many
popular sailing magazines. He and his wife, Olga, cruise aboard their 30-year
old Allied Seawind. They like to point out that they’ve done all the work
themselves with no adult supervision. Don co-authored Sensible Cruising:
The Thoreau Approach and became the authority on boat fix-it projects
with his book, This Old Boat. He is the author of a series of how-to
books in the International Marine Sailboat Library Series. He recently
returned to the subject of cruising with the book, Dragged Aboard –
A Cruising Guide for the Reluctant Mate.

For more on this article: Repowering Part 2 – Don Casey

Repowering, Part 1- the decisions

By Don Launer

Article taken from Good Old Boat magazine: Volume 5, Number 5, September/October 2002.

New engine or rebuild? And should you install it yourself?

Chances are your boat
is like a member of the family. You could no more dispose of it than sell
your only child. But, inevitably, the day arrives when you realize that
your power plant is on its last legs, and there are some important decisions
to be made.

Some boatowners go
to the boatyard, write a check, and say effortlessly, “Call me when
it’s ready.” For most of us, however, it’s a traumatic
moment. After all, repowering an inboard auxiliary sailboat is a lot more
involved than simply dropping a new outboard onto the transom.

For diesel engines,
the symptoms begin to develop years before things become critical. Whereas
your brand-new diesel would start within the first turn, now the cranking
takes longer — and, if the weather is cold, much longer.

When Rudolf Diesel first patented
his engine in 1892, it was a revolutionary idea. His engine used the principle
of auto-ignition of the fuel. This idea, based on the work of English
scientist Robert Boyle (1627-91), was that you could ignite the fuel from
the heat produced by compressing the air in the cylinder. If this compression
were great enough, the temperature in the cylinder could be raised enough
to ignite the fuel-and-air mixture. In modern diesel engines, this compression
ratio is between 14:1 and 25:1, which raises the temperature of the air
in the cylinder to well above the burning point of the diesel oil that
is injected into the cylinder (about 1,000 degrees F).

Compression, then,
is the key to a successfully operating diesel. But when a diesel is up in
years, cylinder walls and piston rings are worn and fouled with deposits,
so they no longer make a good seal. Valves and valve-seats have also become
pitted and fouled and don’t seal properly. Thus, it becomes much more
difficult to get the compression necessary for ignition, especially when
the engine block is very cold and rapidly saps away the heat of compression.

Biting the bullet

When the day finally arrives for you to bite the bullet, there are two
options: get the engine rebuilt or buy a new one. If the horsepower of
the old engine was perfect, if it pushed you through heavy winds and waves
when they were right on the nose, and if that engine has always been freshwater-cooled
and has not had other serious problems, rebuilding that old engine might
be more compelling. Certainly it would be less expensive.

But if your present engine is very old and has had raw saltwater cooling,
chances are that having it rebuilt will not be practical. There will be
rust, frozen bolts, parts to replace, and probably great difficulty in
getting those parts. Even though the cost of rebuilding an old engine
is typically about half that of a new engine, you may very well be throwing
money away on a rebuilding venture. And if you have always felt that you
could use just a few more horsepower to get you through those nasty conditions,
now is a good time to upgrade.

Remember that when you decide
to go with a new engine there are many more costs involved than just the
price of the engine itself. Engines today, which provide the same horsepower
as your old engine, are usually lighter and smaller and rotate at higher
speeds.

These smaller dimensions in
width, height, and length make it almost certain that your engine bed
will have to be rebuilt to accommodate the smaller engine, since its mounts
will probably be closer together.

It’s also important to
know the type of transmission on your new engine. Basically, there are
three different types:

• Parallel is a transmission whose propeller-shaft coupler
  is in line with, or parallel to, the engine’s crankshaft.
• Angle-Drive is a transmission whose coupler is at a downward
  angle to the crankshaft.
• V-Drive is a version in which the transmission is forward
  of the engine and makes a V-turn to drive a propeller shaft leading aft.

Each of these configurations
presents its own problems when rebuilding the engine bed.
The smaller fore-and-aft dimensions will probably also mean that you’ll
need a new and longer prop shaft unless you can set the new engine farther
aft on the beds. Having a new shaft is probably a good idea anyway. After
the old engine has been removed and the old shaft has been slid out of
its stuffing box, you’ll probably see rings of wear in the shaft
where the stuffing box (and sediment) have created grooves. If your old
shaft is more than a decade old, you’ll probably find that the flange
coupling is so frozen onto the shaft with rust that it’s impossible
to free it without further ruining the shaft.

Also, if you didn’t previously
have a flexible coupling or Drivesaver, now is a good time to add this
item, which will help protect your new transmission in the event of the
propeller picking up a piece of wood or a heavy line. If you’re
already using a flexible coupling between the engine and the shaft, chances
are that the bolt holes in this flexible coupling or Drivesaver will not
match your new engine’s coupler, and a new, matching, flexible coupling
will have to be purchased.

As for the propeller, there’s
a 50-50 chance that the new engine may rotate in the opposite direction
from the old engine. (If your present engine turns the prop shaft counterclockwise
in forward gear, as seen from the stern, you now have a left-hand prop.
If the new engine has a clockwise rotation, you need a new prop.)

Even if the direction of rotation
of the new and old engines is the same, chances are that the engine speed,
the horsepower, and the transmission gear ratio of the new engine will
be different from the old. This will probably mean a new propeller of
different pitch, diameter, or number of blades, making your old prop obsolete.

Free consultation

Most engine installation manuals give charts showing the recommended prop
for your particular displacement and hull configuration, and most propeller
manufacturers provide a free consultation service to determine the type
of new prop you’ll need when repowering. Michigan Propellers, for
instance, has a Pleasure Boat Prop-it-Right Analysis Form, which will
suggest the correct propeller for your new engine.

On some boats, the engine and
propeller shaft are deliberately installed at a slight angle off the fore-and-aft
centerline of the boat. This may have been done to offset the tendency
of a single engine to push the stern to one side or the other or to allow
the shaft and prop to be removed without removing the rudder. If your
boat has an offset driveshaft, repowering with an engine whose shaft rotates
in the same direction as the old engine may be preferable. (We have an
offset shaft on our C&C 30. We repowered with opposite rotation and
are satisfied with the outcome. It seems like this should have mattered
more than it did. —Ed.)

The smaller proportions of
a new engine and the rebuilding of the engine bed will also mean that
your present oil drip pan beneath the engine will no longer fit, and a
new pan will have to be fabricated and installed.

There is one complication of
a physically smaller engine that may be overlooked. If you’ll be
using your engine to supply hot water through a heat exchanger, the water
connections on the new engine might well be lower than on the previous
engine. If the heat-exchanger water lines from the engine to the hot water
tank slope upward, an air-lock can develop in the heat-exchanger coil
in the hot water tank that will prevent water flow and, consequently,
heat exchange.
One way to overcome this problem is by installing an expansion tank at
the highest point in the water lines at the hot water tank. The pressure
cap on this tank should match that of the one on the engine, and filling
the water system can be done through the filler cap of the new tank.

Fuel-return line

With diesel engines there’s another thing to consider. Some diesels
had just one fuel line going from the tank to the engine. Most modern
diesels, however, also require a fuel-return line from the engine to the
tank (often called the overflow fuel line). Depending on an engine’s
design, the amount of fuel returned to the tank via this line can vary
greatly.

If you had an engine
with a single fuel line, the chances are that you don’t have a fitting
on top of the fuel tank(s) for this new fuel-return line. This problem
can usually be solved by removing the current air-vent fitting at the
top of the fuel tank and substituting a T-fitting. One side of this T
can then still be used for the air vent while the other side can be used
for the fuel-return line. This problem also will be encountered when changing
from a gasoline engine to diesel.

It’s also likely that
with a new engine, the water, fuel, and exhaust systems may have to be
rebuilt or re-sized. Even if this isn’t the case, when the old engine
is removed is a good time to replace those old hoses.

If you are considering selling
your boat within the next few years, it might be tempting to believe the
value will increase enough to offset the money you have put into a new
engine and its installation. But although a boat will be worth more with
a new engine, the increase in value will probably not equal your investment
when you sell your boat. The same caveat is true if you convert from gas
to diesel. But here we are discussing repowering your boat because you
want to use it for many more years, not with the idea of selling it.

Do it yourself?

Most owners will hand over the repowering project to a knowledgeable,
qualified, and reputable installer. Still, it’s valuable to know
the potential problems along the way. If you have decided to have the
job done professionally, there are several preliminary steps to take:

• Only accept bids from installers who have actually examined your
  boat.
• Consider the reputation of the installer and the yard.
• Ask whether they have installed this type of engine before.
• Ask for references from owners of boats similar to yours who have
  had the same job done.
• Make sure that all associated work is specified on the proposal.
• Be sure that the final installation will conform to American Boat
  and Yacht Council (ABYC) standards.

Some boatowners will want to
tackle the job themselves. If you do your own installation, there are
much greater benefits than saving money. You will end up with an intimate
knowledge of your new installation. This, alone, is a great incentive.

If you decide to do the job
yourself, it’s still a good idea to have a professional in your
corner, someone who is a dealer for your new engine or who has done engine
installations, and whom you can trust, talk to, and order parts from.
If you’re doing your own work, the closer the yard is to your home,
the better. And if you don’t want to tackle the whole job yourself,
you may elect to do just the engine rewiring, the exhaust system, the
water system, or the fuel system, after the new engine has been installed
on its bed and aligned.

Whether you do it yourself
or have the engine installed by a professional, the job requires engineering
judgment and good mechanical skills.

We were fortunate that for
years there was an engine mechanic near us who would give us excellent
and detailed advice whenever we had a do-it-yourself engine job to tackle.
Tom Dittamo, owner of Harbor Marine Engines, in Lanoka Harbor, N.J., has
his business in a marina less than 15 minutes from our home. Tom is also
a Yanmar dealer, so we chose that yard, Laurel Harbor Marina, in Lanoka
Harbor, for our haulout and engine replacement.

We bought our new engine from
Tom six months before beginning our project. He stored it in his shop
at the marina during this time, which allowed me to go in for all the
necessary measurements whenever I needed to. This enabled us to plan well
ahead for our project and purchase all the ancillary gear necessary. (This
early engine purchase, which was suggested by Tom, also saved us 5 percent
on the manufacturer’s price increase that went into effect shortly
after we ordered the engine).

Start early

Changing inboard engines is not a simple project. If you are very adept
at major projects, if you are a good mechanic, if you have lots of time
and patience, and most of all if you enjoy working on boats and this type
of challenge, then you should start doing your homework and putting together
a loose-leaf notebook.

Begin buying the necessary
parts months in advance. I started buying my conversion gear six months
before the start of my project, and that was not too soon. I discovered
that the delivery of a new prop would take six weeks and the longer prop
shaft would take almost as long, even though it was always: “I’ll
have it for you next week.”

It’s important to learn
as much about your new engine as possible before you start the project.
There are many engine distributors who offer one- or two-day seminars
specifically targeted at owners of auxiliary engines. Mack Boring &
Parts Company, which sells Yanmar engines and parts, has one- and two-day
owner seminars on Yanmar engines that are invaluable. These classes are
given at Mack Boring locations in Union, N.J., Wilmington, N.C., Middleborough,
Mass., and Buffalo Grove, Ill. The classes cover the theory of operation,
explain all the parts of your new engine, cover routine maintenance, and
include a hands-on session that gives participants the opportunity to
do routine maintenance on the engine they will actually own, including
adjusting and bleeding it.

Incidentally, one item that
is invaluable in setting up the placement of a new engine on the rebuilt
bed is an engine jig, which can usually be rented from the engine distributor.
The jig consists of light-weight metal framework that locates the proper
position of the engine mounts and shaft alignment. It copies the exact
size and angle of the real engine and can be aligned with the prop-shaft
coupling, revealing whether there has to be any change made in the engine
bed or mounts long before the engine is swung into position.

The alternative to
the engine jig uses another type of alignment method that will be discussed
further in Part 2 of this series, which will
run in the November/December issue of Good Old Boat.

Installation manuals

Nearly all engine manufacturers have comprehensive installation manuals
that are essential for the do-it-yourselfer. These manuals, which should
be part of your repowering notebook, have step-by-step installation instructions,
including alignment procedure; wiring diagrams; engine specifications,
dimensions, shaft and prop recommendations; and fuel, water, and exhaust-hose
requirements. It’s also a good idea to purchase a service manual
for your engine. It will be a handy reference for the future, and it gives
some installation information that isn’t necessarily shown in the
installation manual.

New engines come with their
own instrument panels. If you have an instrument panel recess in your
cockpit, especially one that is molded into a fiberglass boat, make sure
that the new engine’s instrument panel will fit into the old recess.
If it won’t, it might be tempting to try to use the old panel with
the new engine, but this usually is asking for a lot of headaches, including
replacing the tachometer, oil and temperature gauges, and wiring. Some
manufacturers have several panel options of different sizes. Yanmar, in
their GM series for auxiliaries, have three control panels of varying
sizes and options.

Repowering a boat from a gasoline
engine to diesel power needs extra consideration. Diesel engines of equivalent
horsepower are usually physically larger than their gasoline counterparts.
You may find, however, that the Atomic 4 in your boat has much more horsepower
than the diesel you will replace it with. Many smaller boats were powered
with an A4 and a direct-drive transmission. Only half the engine speed
range, and thus roughly half the horsepower, was used. These direct-drive
boats were equipped with very small props.

Bed modification

Even if you’re sure an appropriate diesel will fit in the engine
compartment, you’ll probably need to rebuild or modify the engine
bed. Consider the maximum-diameter prop that can be fitted to your boat
and still have the required tip clearance. Match this against the prop
that the new engine will need. Not all gasoline tanks and fuel lines are
compatible with diesel fuel and, as mentioned previously, a fuel-return
line will also have to be added. The primary water-separator/ fuel filter
will also need to be replaced. In some cases, the prop shaft may have
to be increased in size which, in turn, means a new stuffing box.

Most of us have a pretty good
idea how much power we need, based on the performance of our previous
engine. The old rule-of-thumb for auxiliaries of 2 hp for every 1,000
pounds of displacement is usually pretty good. If you really want to get
into the calculations, then consult Dave Gerr’s Propeller Handbook
or Francis Kinney’s Skene’s Elements of Yacht Design. Another
source of information is at http://www.boat diesel.com on the
web. This site, which provides a wealth of information on diesels, charges
a $25 membership fee. If you click on Propeller/Power/ Shaft Calculations,
you can find the proper shaft size, the power required for a given hull,
and the recommended propeller specifications.

Be sure to check the alternator
options available for your new engine. If your electrical consumption
is high, as is the case with a refrigeration system or a watermaker, be
sure to specify the appropriate alternator when you order the new power
plant.

Engines for an auxiliary must,
above all else, be reliable. When selecting the manufacturer of your new
engine, do your homework. Talk to other sailors who have had an engine
replacement recently and get their opinions. Get information from various
engine companies and local marine mechanics, check out these engines at
boat shows, and talk to the manufacturers’ reps.

When you’re finally back in the water with a new engine, you’ll
feel much more inclined to take that long cruise you’ve been delaying
for years, safe in the knowledge that you have a new power plant of high
reliability for which parts are readily available.

Part
2 of Don’s repowering series, with a focus on installation,
will appear in the November/December 2002 issue of Good Old Boat.

Back To Top

Resources for engines, information

American
Boat and Yacht Council (ABYC)
410-956-1050
http://www.abycinc.org

Beta Marine
252-249-2473
http://www.betamarinenc.com

BoatDiesel
http://www.boatdiesel.com

Harbor Marine Engines
Laurel Harbor Marina
609-971-5797

Mack Boring
908-964-0700
http://www.mackboring.com

Michigan Wheel Corporation
616-452-6941
http://www.miwheel.com

Perkins-Sabre
253-854-0505
http://www.perkins-sabre.com

Vetus
410-712-0740
http://www.vetus.com

Volvo Penta of the Americas Inc.
757-436-2800
http://www.penta.volvo.se

Westerbeke Corporation / Universal
508-823-7677
http://www.westerbeke.com

Yanmar America Corp.
847-541-1900
http://www.yanmar.com

Propeller Handbook, by Dave Gerr
Ask BookMark 763-420-8923
Good Old Boat Bookshelf

Part 2 of repowering article

Repowering, Part 2- replacing the power plant

By Don Launer

Article taken from Good Old Boat magazine: Volume 5, Number 6, November/December 2002.

Tips on how to extract the old one and install the new one

In the September/October
issue of Good Old Boat, we discussed the decisions to be made when
the inevitable day comes that your power plant needs to be either rebuilt
or replaced (Repowering, Part 1: The decisions).
In either case, the engine will have to be removed from the boat. Once
you have decided that engine replacement is the way to go, and you have
made the decisions laid out in the previous article, the actual engine
replacement can begin.

Although the photographs and
text detail the specific procedures on our schooner, Delphinus, most of
the problems we encountered generally apply to all sailboats. We were
replacing a 1980 saltwater-cooled Volvo MD-11C diesel that had a left-hand
prop with a new 2001 freshwater-cooled Yanmar diesel designed for a right-hand
prop. Whether the propeller is left-hand (counter-clockwise) or right-hand
(clockwise), is determined by the direction the propeller turns, as viewed
from the stern, when the transmission is in “forward.” (Usually,
the crankshaft of the engine itself turns in the opposite direction from
the propeller shaft). Although the Yanmar that I decided to use has slightly
greater horsepower than the old engine, its physical dimensions –
height, length, and width, as well as weight – are all less than
that of the old Volvo. This is common with replacement diesels, due to
improved diesel design within the last couple of decades.

Before the old engine can
be removed, all of its connections to the boat must be taken off: the
exhaust, water lines, fuel line, control cables, and electrical connections.
After everything connecting the old engine to the boat has been disconnected,
the screws or bolts holding the engine mounts to the beds can be removed,
and the engine is ready to be hoisted out of the hull.

Difficult removal

It would be nice to think that the old engine can be easily removed. In
point of fact, in fiberglass boats, the engine was often installed before
either the deck mold and/or the interior mold were put in place –
a bizarre construction concept. As a result, some engines have to be removed
through the cabin, while others can be taken out through a removable cockpit
panel. Our boat has a removable cockpit panel, since the centerboard trunk,
on which the schooner-rig’s mainmast rests, is just forward of
the engine compartment doors and eliminates this possibility.

Sometimes an engine can be
removed more easily in sections, such as by first removing the transmission,
and sometimes the old engine can only be removed by lifting it out by
one end. Often, discouragingly, the only way is by cutting out a section
of fiberglass. The same problem may hold true for wooden boats, where
major woodworking reconstruction is sometimes necessary to get the old
engine out of its cocoon.

In order to take out our old
engine, a section of the interior aft countertop in the cabin had to be
cut away. In addition, the Volvo engine and its transmission were longer
than the cockpit hatch opening, and the old engine had to be canted at
a 45-degree angle to get it out of the hull. I had planned to remove the
old Volvo’s transmission, which would reduce the overall length
and make getting the engine out much easier. However, in trying to do
this, I discovered one of the four bolts holding the transmission to the
engine was frozen in place. Its head was stripped, and nothing I could
do would free it. I probably could have drilled it free, but its location,
underneath the transmission in a nearly inaccessible spot, made this almost
impossible.

Yard expertise

When it’s time to remove the old engine, the obvious choice is
between doing it yourself or having the marina do it. Most boatyards have
done this job many times before and have the equipment and expertise to
do it efficiently. If you are hoisting the engine out yourself, it goes
without saying that you must make sure your hoist can handle the weight.
For an engine that has to be removed through the cabin, special equipment,
which most marinas have, is necessary.

With the old engine gone,
the engine compartment can now be cleaned up of old oil and grease. Although
there are many good (and expensive) marine degreasing products available,
you might want to consider using Dawn dishwashing soap, which does the
job as well as or better than anything else. It’s also great for
cleaning up greasy hands and is biodegradable. Once the engine compartment
has been cleaned and becomes more habitable, the old wiring, plumbing,
and exhaust system can be removed and/or reconfigured for the new engine.

Although our installation
was done in the spring of 2002, we purchased our new engine in the fall
of 2001. This was done for two reasons: first, we purchased it just before
a 5-percent price increase; second, having the engine on hand for several
months before the installation was to begin enabled us to check its dimensions,
measure the sizes of the water hoses, exhaust hose, fuel hose, fuel-return
line, and water-heater heat-exchanger hoses, and purchase the necessary
hose diameters and lengths with the assurance they would all fit when
the time came for the hook-ups.

New propeller

Our old Volvo diesel had a left-hand prop, but our new Yanmar has a right-hand
rotation, so early on we bought a new right-hand propeller (a good thing,
since there was a six- to eight-week delivery schedule). We also needed
a new, longer prop shaft, due to the shorter length of the Yanmar, as
well as a flange coupling for that shaft that would be compatible with
the flange on the transmission of the Yanmar. It’s probable that
the flange coupling on your old shaft (as with ours) will be rusted and
frozen in place so it cannot be removed by sliding it back out of the
hull. Fortunately, once the old engine is out of the way, the old prop
shaft and its coupling can be easily removed by sliding it forward, out
into the empty engine compartment. The chances are that the rubber hose
on your shaft-log hasn’t been replaced in a long time, so now’s
a good time. Better yet, consider a dripless coupling, which is easily
installed once the old rubber hose and packing gland have been removed.
(I installed a packless shaft seal manufactured by PYI, Inc.). This investment
will pay dividends in the future by eliminating the awkward contortions
required when readjusting the packing nuts, as well as providing a dry
bilge.

With the old engine out of
the way, this was the perfect time for easy removal of the old water heater
(long overdue), which was in the engine compartment, and the installation
of a new one. The new Raritan water heater, with engine-water heat exchanger
and 120-volt immersion heater, was of similar size to the old Raritan
whose steel case was rusting away. The new Raritan heaters now have plastic
cases and more insulation.

New engine bed

Since it’s probable that your new engine will be smaller than the
old one, the engine bed will have to be rebuilt. This may mean tearing
out the old stringers and installing new ones. If you have a fiberglass
boat, the new beds will have to be built up using fiberglass and epoxy.
If you’re not well acquainted with fiberglass work, it’s
probably a good idea to leave this job to a professional.

We were fortunate that the
mounting width of our new Yanmar was exactly 3/4-inch less than
that of the old Volvo. So we used two heavy-duty, 3/8-inch thick,
3-inch by 3-inch marine-grade aluminum angles bedded in 3M 5200 and through-bolted
to the old fiberglass-and-oak bed. These heavy-duty aluminum beds ensured
that when the mounts were installed they would be true and level.

In nearly all engine conversions,
the different size of the new engine and the rebuilt engine beds will
probably mean that the old oil-drip pan will no longer fit and a new one
will have to be made. I constructed the new one out of fiberglass and
lined it with a replaceable sheet of Oil-Zorb.

Most auxiliary engines are
installed on mounts that have heavy-duty rubber shock absorbers between
the top threaded stud that is bolted to the engine, and the base, which
is bolted to the engine-bed. Usually there are four mounts, near each
corner of the engine. The mounts use nuts and washers on the studs, which
are used to adjust the engine up and down and lock it in place. (The bottom
nut that actually supports the engine is called the “jack nut.”)
The bases of these mounts have holes for the mounting bolts, and one of
the two holes is slotted. These slots allow the engine to be moved sideways
slightly so it can be lined up perfectly with the propeller-shaft coupling.

Different mounts

When preparing to install the engine mounts, be aware that for many auxiliary
engines the engine mounts are different for the front and rear of the
engine or for the port and starboard sides due to the different weight
and dynamic loads imposed on them. These shock-absorbing mounts usually
have a number molded into their rubber, which indicates the rubber’s
hardness. For engines that require different mounts fore-and-aft or side-to-side,
the installation manual will specify their required locations. During
the installation, and in the future, keep oil from getting on the rubber
sections of these mounts, since it can cause the rubber to deform and
swell, eventually resulting in incorrect engine-to-shaft alignment.

Shaft alignment

If you are installing a new engine and retaining your old through-hull
shaft log, the engine-coupling flange will have to be lined up perfectly
with the flange on the propeller shaft. The engine bed must be horizontal
athwartships, with an inclination angle within the allowable limits of
the engine-mount adjusting nuts. Most manufacturers’ installation
manuals give detailed descriptions on this alignment procedure, which
usually is one of two types or a combination of both.

To determine the centerline
of the propeller shaft, its height, and its inclination, a pointer is
bolted to the propeller-shaft flange, with a string coming out at shaft-center.
This string has a fish-weight tied on the free end, and this weight goes
over a piece of wood that is temporarily clamped to some point farther
forward.
When the propeller shaft is rotated, this free-end piece of wood is moved
until the pointer circles the string evenly. The position of this string
now becomes the centerline extension of the propeller shaft, from which
engine-bed construction and engine placement measurements can be made.
Installation instructions recommend that this pointer and string be fastened
directly to the propeller-shaft flange, rather than to an intervening
flexible coupling or “Drive-Saver,” which could introduce
an error.

Although the construction
of a new engine bed and alignment of the new engine can be done directly
from measurements to this centerline string, a much easier and less time-consuming
way of creating the new engine bed and aligning the engine is through
the use of an engine-bed alignment jig. These jigs can sometimes be rented
from an engine distributor for your particular engine, greatly simplifying
the engine-mount placement measurements. As in the previous step, the
string from the center of the propeller shaft passes through alignment
holes in the jig, and the engine mounts, which are bolted onto the jig,
can be located perfectly on the new engine bed, with the assurance that
the propeller shaft flange and the engine transmission’s flange
will match very closely when the new engine is installed.

Check tolerances

Once the engine mounts have been fixed to the new bed and the engine has
been installed, it’s time to check the coupling tolerances between
the two flanges. Mismatches between the two surfaces (the flange on the
engine and the flange on the propeller shaft), should be compensated for
by adjusting the motor mounts, which can move the engine up or down an
inch or more. The slots in the engine mounts also allow you to move the
front or rear of the engine to one side or the other to match up the two
flanges. Using a feeler gauge around the periphery between the two flanges,
you can adjust the engine mounts so that the two flanges mate to within
1/1,000 inch. Note that these tolerances should be checked between
the flanges themselves, and not with an intervening flexible-coupler or
“Drive-Saver.” Once the two flanges match perfectly, the
flexible coupling can be added, and, with everything lined up, the bolts
on the flanges are tightened. This shaft alignment is vital for preventing
Cutless-bearing wear, transmission damage, and vibration.

A new engine installation
is usually performed on land. It’s important to realize that when
a shaft alignment is done on land, the alignment can change after the
boat is back in the water with the mast stepped and the rigging tensioned.
On a new engine, this alignment can also change during the first few days
or weeks as the rubber in the new engine mounts compresses to its final
size. Some installation manuals suggest that the jack nuts on the engine
mounts be raised one turn above perfect alignment to compensate for this
inevitable rubber compression.

Anti-siphon valves

If the raw-water output from the engine that goes into the exhaust-mixing
elbow is below or close to the boat’s waterline (when level or
heeled over), it’s imperative that an anti-siphon valve be added.
Without this valve, after the engine is turned off, water can continue
to siphon into the exhaust system, eventually backing up into the engine
itself and causing major damage. The anti-siphon valve allows air to enter
the system when there is a suction, which occurs during siphoning, but
the air valve closes when pressure is present, as when the engine is running.

There are many types of anti-siphon
valves, made from various materials. Some have connections for a small
tube that allows the few drops of overflow water to go directly to the
bilge rather than drop on top of the engine. This can prevent fresh water
or corrosive salt water from attacking the top of your new engine. This
overflow tube has another advantage: by blowing into the tube you can
determine whether your siphon-vent is clogged or stuck.

Engine connections

When the engine is in place, it’s time to connect the fuel supply
line, fuel return line(s), water system, exhaust system, electrical system,
and control cables. If hoses, control cables, and wiring in the engine
compartment haven’t been changed in a while, now is a good time.

When it comes to determining
sizes of fittings and machine screws on your new engine, you must realize
that there are three primary measuring systems in use around the world,
metric standards, USA (inch) standards, and British (inch) standards.
As the world moves toward metric standards, sailboat power plants will
be increasingly built to these standards.

Fortunately there are now many
places in the United States that can supply metric tools and machine screws.
But even on an engine built to metric standards, there are anomalies.
Strangely, most countries that use metric standards, both in Europe and
in Asia, use the British (inch) standard for measuring pipe fittings.
I discovered this contradiction when installing my metric system Yanmar
engine. Almost everything on this engine is metric, but the threads on
the engine for the water fittings that feed the heat-exchanger for the
on-board hot water tank are British (inch) standard.

British standard pipe-fittings
come with either a cylindrical (parallel) thread or with a tapered thread.
My Yanmar engine demanded a fitting with British standard tapered threads
(which are designated in Japan, and in the Yanmar shop manual as “PT.”
Thus, a designation of “PT-3/8” (as shown in the
shop manual) means that the fitting is a British standard 3/8-inch
tapered pipe fitting.

No fittings

The Yanmar engine
has two plugs that can be removed to accept the hose-fittings for the hot-water
tank’s heat exchanger. Although Yanmar sells the hose adapters that
fit these threads, the fittings had been on back order for several months
and were not available when I was installing my new engine.
Luckily, I discovered Maryland Metrics http://mdmetric.com/ on the Internet. This company sells a wide range of metric tools and fittings
as well as British standard and American standard pipe fittings and adapters.
They had adapters in stock that went from the British standard tapered
3/8-inch pipe thread (PT-3/8) on the Yanmar to a U.S. standard 3/8-inch
pipe-thread, which solved the problem nicely. Once I had converted to
the U.S. thread, elbows and hose adapters were readily available.

Incidentally, Maryland Metrics
has a wonderful website describing the threads in all three systems. They
also have a huge inventory of nuts, bolts, parts, adapters, and metric
tools. For my very small order for two adapter fittings, they couldn’t
have been nicer or more cooperative in helping me solve my problem.

Final preparations

When everything has been completed, it’s time to fill the crankcase
and the transmission with the oils specified by the manufacturer. Before
doing this, however, check the oil levels, since many manufacturers supply
the new engine with oil already in the crankcase and transmission. This
is an especially important check with diesel engines, since too much oil
in the crankcase can cause a runaway engine. With freshwater-cooled engines,
fill the engine’s heat-exchanger with a 50/50 solution of water
and anti-freeze, as per the manufacturer’s instructions. Many manufacturers
recommend that the water used with the anti-freeze be distilled water,
since there’s no telling what chemicals might be in city water.

For diesel engines it now will be necessary to bleed the fuel system,
otherwise the engine won’t start. This bleeding is usually done
at two places in the fuel supply system as well as at the injectors of
each cylinder. These locations will vary from manufacturer to manufacturer
and will be described in the owner’s manual. Once you have located
these points it’s a good idea to paint all of these bleed-points
with white paint. It will make it a lot easier to locate them at some
time in the future when you accidentally run out of fuel and you have
to do a bleeding job under less than ideal conditions. It will also make
it easier to bleed the system each time you change the engine’s
fuel filter.

Check liquid levels

After the engine is run for its first test – no more than a couple
of minutes – the levels of oil in the crankcase and transmission,
as well as the cooling-water level, must be checked. As the fluids are
distributed throughout the engine and heat exchanger, levels can drop.

Most diesel manufacturers
recommend that if your engine hasn’t been used in a few days, it’s
a good idea to pre-lubricate it before starting. For engines that have
a manual Stop control, this can be done by holding out the Stop control
while turning the engine over with the starter for about five to 10 seconds.
If the engine hasn’t been used in a really long time, wait 30 seconds
and repeat the procedure. This will distribute oil throughout the engine.
It’s also a good idea, after starting, to let the engine run at
mid-range for about five to 10 minutes before putting it under load.

When stopping, let the engine
cool down by idling it for about five to 10 minutes, then, just before
stopping the engine, give it a burst of power to blow out any carbon in
the cylinders.

When our boat was finally
back in the water after the new engine had been installed, I was hoping
that it would be a calm day for the one-hour motor-trip from the marina
to our home dock, but this was not to be. When I came out of the marina
I had 20 knots of wind right on the nose and a high chop. It was literally
a shake-down cruise. But the new installation performed flawlessly, and
I was able to head home at hull speed.

This new engine installation
should be good for the next 25 to 30 years. I just wish that I could be
good for that long.

By Jerry Powlas and Dave Gerr

Article taken from Good Old Boat magazine: Volume 1, Number 2, September/October 1998.

Guidelines for evaluating and installing wet exhausts

The most popular sailboat exhaust system today is a wet exhaust system
which includes a waterlift muffler. This system offers many advantages
and seems deceptively simple. Almost all engines are cooled with seawater,
either directly or though a heat exchanger. The seawater must be discharged
after it has picked up the engine heat, so it is logical to inject it
into the engine exhaust. This cools the engine exhaust so it can be routed
through the boat without too much concern for the parts of the boat that
it passes near and through. Wet exhausts are the best choice for the majority
of sailboats, but they can cause trouble if not properly designed, installed,
and maintained.

At first
glance it looks like all that is required is to plumb the parts in series
in the proper order. That approach, however, will likely cause trouble.

We assume
that naval architects and boatbuilders know how to design and build a
wet exhaust system. We speculate that wet exhaust problems have come mainly
from boats that have been modified during repair or converted from other
types of exhausts by owners or technicians who did not thoroughly understand
wet exhausts. That could easily happen for two reasons. First, not all
boats are configured to allow a system to be installed which complies
with the guidelines; and second, the requirements are more complicated
than they appear.

The following
outline lists common wet exhaust fault modes. The most serious problems
with wet exhausts involve seawater working its way back into the engine,
where it gets into the cylinders and flows past the rings into the crankcase.
This kind of water penetration may require engine rebuilding or replacement.
In extreme cases after flooding the engine, a defective system can even
flood and sink an unattended boat.

Water in engine fault modes (See Figure Four.)

1. 1. Siphon faults
      1. Water siphons from the cooling water seacock past the raw-water
         pump into the injection elbow when the engine is off. It fills the muffler
         and floods the engine.
      2. Water siphons backward up the exhaust piping, fills the muffler, and
         floods the engine.

1. Heavy weather faults
   1. Following seas force water back up the exhaust system where it fills
      the muffler and floods the engine. The use of a stern-deployed drogue
      can aggravate this problem. b. The boat heels or pitches enough to make
      the muffler higher than the engine, so water flows from the muffler into
      the engine.
   2. The boat pitches enough to get the raw-water intake out of the water
      frequently and for long enough periods to starve the exhaust system of
      the cooling water it needs causing the plastic and rubber parts to overheat
      and fail.

Other failure modes

1. The raw-water circuit fails from:
   1. Plugged intake.
   2. Plugged raw-water filter.
   3. Pump impeller failure (most likely of all failure modes).
   4. Plugged water line from pump to injection elbow (pieces of impeller).
   5. Plugged injection elbow (rust, scale, pieces of impeller).

If the raw-water circuit fails, the exhaust system will overheat very quickly. Most of the exhaust parts on most boats will not withstand the overheating caused by a raw-water system failure. The following can occur before the engine overheats enough to get your attention:

1. Hoses burn out.
2. Muffler melts, if plastic.
3. Muffler liner separates, if plastic or rubber-coated steel.

2. 2. Corrosion can cause failures of:
      1. Injection elbow.
      2. Exhaust hose (it is wire-reinforced).
      3. Waterlift muffler (if steel).

2. Freeze damage
   1. If the muffler is steel.

Wet exhausts
are not foolproof, but given proper design, installation, and maintenance,
they are a good choice for most sailboats.

Siphoning, velocity pressure, water head

Siphoning, velocity pressure, and water head (pressure) are three concepts
that are important in understanding wet exhausts.

Siphoning
will occur when you put a small hose overboard, suck on it until it is
full of water, and then bring the inboard end into your boat below the
water level. (See Figure One.) The water will flow up the hose and down
the other side, filling your boat until it sinks. No pumping is required.
Any bilge pump through-hull that is ever below the waterline can cause
siphoning after the bilge pump fills the piping with water. The pump shuts
off, and the flow reverses. This is a fairly common problem. Think in
terms of the heeled waterline, the waterline with full cruising stores,
the waterline when the boat squats under power, or a combination of these
factors.

Water
head is a way to describe the pressure in a system. In this term, the
word head equates to height. The pressure at the base of a water tower
is a function of the height of the water in the tower. (See Figure Two.)
Sometimes very low pressures are described in terms of inches of water
column. These pressures can be converted to pounds per square inch, which
is the more familiar unit of measure. The conversion is 27.68 inches of
water column equals one psi.

Velocity
pressure is a way of expressing the speed of a fluid in terms of the pressure
it causes when it strikes something. This phenomenon is used to make simple
speed-measuring devices that measure the height of a column of water caused
by the velocity of the water flowing past it. (See Figure Three.) Note,
six knots is equal to a velocity pressure of about 19 inches, and in Figure
Three the pressure is measured directly in inches of water column.

Figure
Four shows a complete wet exhaust system and is similar to other diagrams
published on this topic. The discussion which follows is absolutely unnecessary
if you have a boat that allows the specified features, including dimensions,
to be followed faithfully.

The important
point is that some good old boats were not designed with this type of
exhaust system in the first place, and either their machinery spaces will
not allow the installation of this type of exhaust per the specifications
of Figure Four, or the persons making repairs or modifications did not
completely understand the requirements. You may want to check your boat
to see how closely your current layout complies with the requirements
of Figure Four.

In studying
your boat and the diagram, note that features are positioned relative
to each other and relative to the waterline. You can find the waterline
in your machinery space by making a siphon like the one shown in Figure
One. Remember you are finding the at-rest waterline by this method. Sailing,
heeling, powering, pitching, and rolling will all change it.

Now let’s
follow the water into the boat and back out again. The water enters by
a through-hull and seacock and flows through a raw-water filter. The through-hull
may include a scoop. If there is a scoop, it will develop some velocity
pressure when the boat is moving. (Six knots produces about 19 inches
of water column pressure.) An allowance may be needed when considering
other aspects of the system design if there is a scoop facing forward.
Some systems are built without the filter, but it is a good investment
because it protects the raw-water pump. The water flows through the raw-water
pump and either through a heat exchanger or two, or through the engine
itself. After leaving the engine, it is discharged into the exhaust.

The injection
point should be 4 inches (minimum) below the exhaust manifold exit point.
(See Dimension H on Figure Four.) This distance is required to keep the
steam and other nasty chemicals created at the injection point from attacking
the exhaust valves. The engine manufacturer knows this and will provide
an arrangement that protects the engine.

The injection
point must also be located relative to the waterline. If it is high enough
above the waterline, a vented loop is not required. The minimum height
varies depending on which authority is consulted. We found minimums from
6 to 16 inches recommended. This may be because a scoop at the through-hull
can raise the water level in the piping, leading to the injection point
when the boat is sailing (engine off). In addition to allowing for velocity
pressure,it is necessary to allow for maximum loading, rolling, and pitching
mo tion.

If the
injection point is closer to or below the waterline than the allowance,
there is the potential for a siphon to form. This siphon is prevented
from forming if the raw-water pump does not leak. There is the risk, however,
that it will leak. Small leaks may occur at the rotor sides or tips, and
the common failure mode for this pump is for the lobes on the impeller
to break off and be carried downstream to do mischief elsewhere in the
system. The lobes don’t all break off at once, so the pump may deliver
enough water to keep the engine cooled, but it will leak when the engine
is not running. Even a fairly small leak can, over time, flood the muffler
and then the engine.

The vented
loop shown in Figure Four breaks this siphon. The top of the arch of the
loop should be at least 6 inches above the waterline. Some authorities
say 12 inches minimum, with 16 inches being better. Remember, if you have
a scoop at the through-hull, it will raise the level of the water in this
part of the system by virtue of its velocity pressure. As mentioned above,
depending on how fast your boat is, you need to allow for this. At the
top of the arch of the vented loop there must be either a siphon break
valve, or an additional tube extended from a tee.

In saltwater
service, the siphon break valve may become clogged with salt crystals
and either become inoperative (not break the siphon) or leak constantly.
The constant leak failure mode can result in spraying seawater around
in the machinery space. This seawater is needed to cool the exhaust. For
these reasons, some authorities recommend dispensing with the siphon break
valve and locating a tee in the line vented higher up, such as in the
cockpit.

Even
if there is a tee, with a tube extending from it to a higher location,
it is necessary for the top of the arch in the vented loop itself to be
positioned 6 to 16 inches above the waterline. If it is not, a siphon
may still form in some circumstances. In other words, extensions from
the tee don’t count against the 6 to 16 inches requirement. The extension
tube from the tee should extend higher than any other point in the system.
This can be a problem in some boats.

Before
we leave this part of the system, we should mention that a cranking engine
is pumping water into the exhaust system. If it cranks a lot and does
not fire, the muffler may fill up with water and eventually flood the
engine. Some authorities recommend closing the cooling water seacock during
prolonged cranking such as when bleeding air out of injectors, the first
start after lay-up, or when troubleshooting a reluctant engine. As soon
as the engine starts, quickly open the seacock again. If the muffler has
a drain, it could be left open instead until the engine fires and then
be quickly closed.

The distance
from the injection point to the muffler inlet is specified by various
authorities as 10 or 12 inches minimum. This is intended to be both a
minimum length and a minimum vertical distance. We think that on some
significant number of good old boats this is the dimension that will be
most difficult to comply with.

On Mystic
(our C&C 30), the machinery space will not allow the muffler to be
much lower than the exhaust outlet because the bottom of the boat slopes
up sharply behind the engine. Worse, the boat was designed for an Atomic
4, which has the exhaust on the port side. The Bukh Pilot 20 diesel that
was fitted later has the exhaust on the starboard side. The original muffler
platform was used, so the muffler is on the opposite side from the exhaust.
Moving the muffler platform would have been complicated because the cockpit
drain and raw-water through-hulls and seacocks occupy the space where
the muffler should go on the starboard side. That may be why the mechanics
who did the conversion to diesel did not put the muffler on the same side
as the exhaust. When our boat heels to starboard, the muffler is elevated
above the engine, providing an opportunity for it to pour water into the
engine.

Ideally,
the muffler would be mounted directly behind the engine exhaust so it
is not elevated above the engine as the boat heels. We were told by one
knowledgeable person that Dimension A is also the minimum distance the
exhaust gases must travel to ensure that they are cool enough to enter
a plastic muffler without damaging it. This seems logical. All the cooling
will not occur at the exact point of water entry, and the process of heat
exchange will take some time, and therefore distance, to be completed.

As
we said, the space for an 8 to 12 inch (minimum) vertical drop from the
engine to the muffler is not available on some boats. There are two possible
solutions to this problem: both involve some manner of exhaust riser.
Where a short riser is required, engine manufacturers can provide an exhaust
riser that is a water-jacketed exhaust pipe which lifts up and turns back
down. After the downturn, the jacket water is injected. Contact your engine
manufacturer about this option. If you have room for it, it may be a very
good way to obtain the minimum drop distance.

Where
a larger lift from the manifold is required, it may be necessary to run
a dry unjacketed (very hot) insulated pipe to another location, where
either a conventional exhaust elbow is fitted or a standpipe is used.
See the companion article by Dave Gerr which deals with several special
versions of wet exhausts that can be used to overcome layout problems.
Remember as you contemplate variations on this theme, when the flow reverses,
the drop becomes a rise, and this rise is what protects a flooded muffler
from dumping into the exhaust manifold when water backs up in the hose
leading from the muffler to the exit.

Dimension
C is the vertical rise from the bottom of the muffler to where the hose
turns back down. This is the lift. We found maximum dimensions for this
lift of 40 to 48 inches, with 20 inches being cited for turbocharged engines.
Some literature seems to suggest that the height of the lift determines
the exhaust back pressure in some simple way so that (for example) a 48-inch
lift would give a 48-inch water column back pressure. It seems logical
that if there were enough water in the muffler to fill the lift pipe,
and if the pressure were slowly increased on the engine side, as perhaps
in a case of cranking and not firing, this reasoning might pertain. Once
the engine is firing, however, it is doubtful that there would ever be
a solid column of water in the lift pipe. With exhaust gas flowing in
the lift, much more complex things are happening. The flow in the lift
is probably a chaotic mixture of gases and liquids. One source said that
engine manufacturers know this and are not too worried about this maximum
lift dimension. In individual cases, it would be best to contact the engine
manufacturer and follow the manufacturer’s guidelines.

Ideally,
the hose from the muffler exit to the top of the lift is vertical, not
slanted. The reason for this is that a vertical pipe achieves the maximum
rise with the least volume. The concern here is that the water in the
lift pipe will fall back into the muffler when the engine shuts down.
This is a critical issue. The muffler volume must be large enough to accept
the water that falls out of the lift pipe. The rule of thumb is that the
muffler should have at least 130 percent of the volume of the lift pipe.
Note here that if the muffler is fairly well filled from water falling
back from the lift pipe, it is much more likely to cause mischief in other
ways. At the upper end of the lift pipe the exhaust hose should slope
down toward the exit through-hull. Note: the intent is that everything
from the top of the lift pipe either drains to the muffler or drains overboard.
At least that is the way the story goes for a system without an exit gooseneck.
Some authorities go so far as to say that there must be no sags in the
sloping pipe from the top of the lift to the exit through-hull. The sags
would allow some water to be trapped, while a straight sloping pipe would
drain overboard.

The alternative
gooseneck shown in Figure Four is a variation sometimes seen where there
is not only a sag, but in fact a large trap. The hose loops down and back
up and down again. The gooseneck provides some added protection from pooping
seas by forcing the water to lift up the gooseneck to get into the system.
We found one reference that suggested a minimum dimension of 16 inches
from the top of the gooseneck to the waterline. One manufacturer makes
a plastic gooseneck that looks like it might take less space than a looped
exhaust hose. Because the price of exhaust hose is fairly high, it might
be less costly as well.

Returning
to the top of the rise again (See Dimension D), the minimum dimension
from the top of the lift to the waterline is 12 inches. More is better,
and 18 inches is recommended by some authorities. Dimension D should be
viewed as a minimum vertical dimension. Its purpose is to provide resistance
to water flowing back up the hose to the top of the lift and then falling
into the muffler.

The exit
through-hull should be located above the waterline. Suggestions for this
dimension vary from 3 to 6 inches to the centerline of the exhaust pipe.
(See Dimension F.) The reason it is desirable for the exhaust to exit
above the waterline is so it can’t create a siphon. The reason the outlet
is not located very high, just below deck level for example, is to help
prevent exhaust fumes from coming back into the boat. Because it is fairly
low however, it will be submerged by waves, and the pitching motion of
the hull. The American Boat and Yacht Council (ABYC) recommends that the
outlet be located near the intersection of the hull and transom because
this also helps prevent exhaust fumes from getting back into the boat.

The total
length of the piping from the muffler to the exit is shown as Dimension
L. Very long piping runs increase back pressure. This hose should have
a length of less than 30 times the exhaust line diameter as it enters
the muffler from the engine. For example, for a 1H-inch diameter hose,
the run shouldn’t be over 45 inches total length from the lift outlet
to the throuh-hull. This run is commonly much longer than 48 inches. If
the run has to be longer, you may need to make the hose diameter larger.
(These long runs and larger hoses will also require a larger muffler canister.)
For runs up to 60 times exhaust diameter, increase the hose diameter by
20 percent. Still longer runs are possible, but you must increase diameter
still more and check with the engine manufacturer about the maximum acceptable
back pressure. As with any exhaust, you should use as few bends as possible
with the largest radii possible; tight bends also increase back pressure.

If, when
inspecting your system, you find that your hoses are too long and should
be larger in diameter according to the rules of thumb just mentioned,
it would be a good idea to get an opinion on your specific system from
your engine manufacturer. You may even want to check back pressure in
actual operation before buying all that new larger diameter hose.

Feature
J on Figure Four is a valve which is intended to be closed when sailing
in rough seas. It should be able to withstand the temperatures involved
(200 degrees Fahrenheit minimum) and should be located where it can easily
be reached in rough weather. For this reason, it is unlikely to be located
at the through-hull and should not be thought of as a seacock. While we
understand the intent of this valve, we have the following concerns about
its installation and use:

1. It is not a passive device that tends to work automatically. The crew
   must close it when conditions warrant and must open it before starting
   the engine.
2. If the crew tries to start the engine with the valve closed, the best
   thing that could happen is for the engine not to start.

For these
reasons, we consider the valve as an option of last resort to be used
only if the geometry of the boat does not allow a layout that can function
properly without it.

Mysteries and nuances

With
the engine off:
Imagine the boat being pushed down by the stern so the exit through-hull
is submerged. Or imagine the exit through-hull being slapped by a large
wave. Combinations of these two cases will occur when the boat is pitching
in a large following sea. We speculate that some interesting things will
happen in this situation.

A trapped
air pocket will form in the tube between the muffler and the exit. The
pressure of the pocket will be a function of how fast the waves hit the
stern, and how deeply the stern is pushed down by pitching. In the worst
case, velocity pressure and water column pressure will add together. It
is not unreasonable to assume 10 knots for the wave velocity (it takes
only Force 6 for this) and, thus, 51 inches of water column pressure increase.
If the stern is pushed another 6 inches below the water, the total reverse
pressure would be 57 inches of water column pressure.

Now let’s
return to how full the muffler is when the engine shuts off and the water
in the lift column falls back into it. If the muffler is not very full,
air is pushed into it and out the inlet toward the engine. If seawater
did not manage to push its way to the top of the lift column, the muffler
does not gain any water, and the water in the sloped section from the
top of the lift drains back out, ideally before the next pitch/wave slap.

If the
muffler is nearly full, the pressure in the piping downstream of the muffler
will force water, not air, out the muffler inlet toward the engine. Now
consider Dimension A again. If this dimension is a vertical dimension,
the water must lift against gravity to reach the engine. If it is a sloping
horizontal dimension, the lift is not great, and the engine is more likely
to be flooded. The dimension should be a vertical dimension, but in some
boats that is not possible.

Figure
Four shows an alternative in which a gooseneck is located at the end of
the piping before the exit through-hull. One manufacturer cites a minimum
dimension of 16 inches from the top of the gooseneck to the waterline.
With a gooseneck at the exit, the water must lift against gravity to the
top of the gooseneck before it can enter the system to stay. This seems
like a very positive improvement.

Significance of dimensions

Dimension A

12-inch minimum vertical, 12-inch minimum total, sloped downward H inch
per foot minimum. (The slope is not likely to be this small if the other
criteria are met.)

Minimum
vertical dimension from the injection point to the top of the muffler.
(Also) minimum total distance from the injection point to the top of the
muffler.

Significance:
When the engine is running, this minimum total distance gives the water
time to mix with the exhaust gases and cool them. This minimum is necessary
to protect plastic and fiberglass mufflers from excessive temperatures.

When
the engine is not running, this minimum vertical distance helps retard
the flow of seawater from the muffler to the engine where it will damage
the engine.

If the
minimums cannot be achieved, the alternatives are:
1. Use a special exhaust riser supplied by the engine manufacturer to
increase the vertical distance. (Yanmar calls this a “U mixing elbow.”)
2. Run some dry (hot) exhaust piping to some other location where there
is space to get the height needed, and then use a mixing elbow or a stand
pipe. See Dave Gerr’s article on Page 20 for alternative exhaust systems.
3. In the worst case, where there is no space for any of these options,
a water-jacketed or dry exhaust system may be the only alternatives.

Dimension B

12-inch minimum, 16 inches is better. Minimum vertical distance from the
waterline to the bottom of the vented loop.

Significance:
If the injection point is above the waterline (6 to 16 inches are quoted
figures), you don’t need a vented loop. Remember that a scoop at the through-hull
takes away from this margin, as do heeling, pitching, squatting, and loading.

A siphon
break may be used in the vented loop, or a tee and extension may be used
with no valve. Siphon valves may become salt-encrusted and leak. Tees
and extensions should vent to a point higher than any other part of the
exhaust system.

Dimension C

42 inches maximum.
20 inches maximum with turbocharger.
Maximum vertical distance from the bottom of the muffler to the top of
the lift.

Significance:
When the engine stops, the top of the lift divides the water in the system.
The water in the lift flows into the muffler, (which must be able to hold
it all) and the water in the down-stream piping flows to the through-hull.
Excessive lift
is thought by some authorities to cause excessive back pressure. Other
opinions minimize the significance of this.

Dimension D

12 to 18 inches minimum (depending on which authority is consulted).
Minimum vertical distance from the top of the lift to the waterline.

Significance:
When the engine is off, and water is being forced backward into the system
through the through-hull from following seas, or the through-hull is forced
under water from the motion of the boat, or some combination of these,
this lift helps to keep water from getting over the top of the lift and
draining into the muffler. Sometimes this protection is enhanced by using
a gooseneck as shown with Dimension I.

Dimension E

12 inches minimum (this dimension is redundant if Dimension D is complied
with).
Minimum vertical distance from the top of the lift to the through-hull
(similar to Dimension D).

Significance: When the engine is off, and water is being forced backward into the system
through the through-hull from following seas, or because the through-hull
is forced underwater from the motion of the boat, or some combination
of these, this lift helps to keep water from getting over the top of the
lift and draining into the muffler. Sometimes this protection is enhanced
by using a gooseneck as shown with Dimension I.

Dimension F

3 to 6 inches minimum (depending on which authority is consulted).
Minimum vertical distance from the waterline to the through-hull.

Significance:
When the engine is off, it is desirable to have the exhaust exit point
above the waterline so that it cannot start a siphon. Safety margins are
eroded by heeling and loading.

When
the vessel pitches, the through-hull can be submerged, and pressure formed
in the piping that will try to force air (or water) backward out of the
muffler and into the engine.

Some
successful layouts have been built that have the exhaust outlet lower.
Powerboats sometimes have it below the water.

Dimension H

Minimum distance from the exhaust manifold to the injection point.
4 inches minimum

Significance:
Highly corrosive chemical combinations form at the injection point.
The intent of this dimension is to keep these from reaching the engine
exhaust valves and guides. In most cases, the engine designers will take
care of this parameter.

If the
dimension is too long, it may be necessary to insulate the part of the
exhaust that is dry (and hot).

Dimension I

Minimum lift in (optional) gooseneck.
16 inches minimum

Significance: Where this last gooseneck is used, it provides added protection against
water flowing backward into the piping and reaching the muffler. It is
interesting to note that not all authorities recommend this feature. We
think it is a good idea.

Dimension L

Maximum length from muffler to exit.
30 times manifold outlet diameter. An alternative is to increase hose
size.

Significance: It may be necessary to increase the diameter of the piping to reduce resistance.
See the North Sea Exhaust description in Dave Gerr’s article.

From
the forgoing, you can see that the issues associated with wet exhausts
and waterlift mufflers are not simple, and it is possible for a boat to
be configured so that a “conventional” installation is not possible.
We would expect this to be more common in the case of good old boats that
were not designed for a wet exhaust in the first place. We would also
expect this to be more of a problem for fin-keel designs without a lot
of depth from the engine compartment to the transom. In a companion article
in this issue, Dave Gerr explains some of the other methods for dealing
with wet exhausts that cannot be laid out according to the recommendations
we have presented here.

A quick disclaimer

We have tried to present the most detailed information possible on this
topic. The application of a wet exhaust and waterlift muffler can be complex.
As we have said, not every boat has the space available for the “standard”
layout. Some boats don’t even have spaces that are suited to the alternative
layouts. It is important to contact your engine manufacturer and the manufacturer
of your exhaust components for specific parameters and to resolve any
questions or doubts with these sources. One muffler manufacturer said
they regularly provide this information to their customers, and it is
likely that the other manufacturers will as well. We have presented this
information believing that if you know the intent of each characteristic
and parameter in the system, you will be better prepared to evaluate variations
that may be needed to accomplish the same intent.

In the
end, as in so many things on your boat, the responsibility for the safety
and good functioning of your exhaust system is yours.

By Cory Carpenter

Article taken from Good Old Boat magazine: Volume 4, Number 4, July/August 2001.

A 27-year-old outboard starts a newer, deeper life

I bought Brushfire, my 1975
San Juan 24, from the Sea Scouts. Before I agreed to the deal, the
Sea Scouts offered to throw in an outboard as a sweetener. The motor
they dug up for me was a 7-hp Eska of 1973 vintage, a two-cycle with
an integral three-quart fuel tank.

It ran well enough once I did some research and discovered that it
wanted a 24:1 fuel-to-oil ratio, but I found that even with my 180
pounds as far aft as possible and Brushfire’s scissors-style
motor mount at its lowest setting, the Eska’s cavitation plate
was barely below the surface. The whole prop came out of the water
with any kind of wave action and the motor would race madly with a “www-AH,
www-AH, www-AH,” like a hydroplane running through chop. My original intention was to use the Eska just long enough to get
Brushfire about 3-1/2 miles down the Columbia River from the Sea Scouts’ base.

I figured I would return it to the Scouts and treat myself to a new
long-shaft Honda four-stroke. Then I started checking prices . . .
and concluded that it wouldn’t be such a bad thing to have an
outboard from the same era as the boat! In the course of researching long-shaft outboards on the Web, I happened
upon Bay Manufacturing of Milan, Ohio, which makes shaft-length conversion
kits for Mariner, Mercury, OMC, and Yamaha outboard motors, but not
for 27-year-old Eskas. Looking at the pictures on their Web page
caused me to wonder what it would take to do my own long-shaft conversion.

The motor

My Eska is a model 1747-C. It uses a Power Products/ Tecumseh recoil-start,
two-cycle, air-cooled power head, much like a lawnmower engine’s
except that the exhaust port is on the bottom of the cylinder, rather
than the side. I’ve seen discussions on the Web that indicate
this motor was also sold under the Sears Gamefisher and Ted Williams
trademarks. It has a spring clutch to engage the driveshaft, providing
neutral and drive gears. (Mine was frozen with rust, and the motor
had to be started in drive. Soaking the clutch in kerosene for a week
or so helped free it up.) For reverse, you swing the motor all the
way around and, while hanging precariously over the transom, you try
to remember which direction to twist the throttle. In drive, a small
pump provides cooling water to the exhaust manifold/adapter plate that
mounts the engine to the lower unit of the motor. I obtained a service manual from Certified Parts Corporation, which
purchased the outboard and trolling motor divisions of Eska in 1988
and still provides most parts for these units. Some study of the
exploded diagrams in the manual showed that, given the proper tools,
it would
be fairly straightforward to construct a shaft extension. Conveniently,
the housing containing the propeller shaft, gears, and water pump
separates from the main section of the column just above the cavitation
plate.The
cooling-water tube merely connects to the pump with a friction fit
into an O-ring, while the top end of the driveshaft fits into the
clutch on the engine’s output shaft in much the same way, torque
being transmitted by splines. Because of this simple design, all I
needed to do was add length to the cooling-water tube, fabricate a
new driveshaft, and build an extension fairing, a shell that would
conform to the cross-section of the column where it joined the gear
housing. I decided that an additional six inches would be about right. For the best corrosion resistance and electrolytic compatibility
with the rest of the motor, the new parts should have been fabricated
from
aluminum and stainless steel. Because I wasn’t willing to go
to the trouble and expense of obtaining the ideal materials, because
my MIG welder won’t handle aluminum wire reliably, and since
this project was experimental anyway, I used mild-steel stock that
was lying around my garage for the major components of the extension.

The long driveshaft

To avoid doing unnecessary work in case the project proved infeasible,
I started with the driveshaft, the most critical piece of the extension
in terms of tolerances. The original driveshaft is a 7/16-inch
steel rod approximately 24 inches long, splined at each end and keyed
at the lower end to drive the water pump. (I note that the original
shaft will deflect the compass aboard Brushfire, so it may not be stainless
steel.) What I had on hand was 1/2-inch rod, but since the center
of the shaft runs free inside the column, the diameter is only critical
at each end. After cutting it to length, I turned the ends of the 1/2-inch
stock down to 7/16-inch. Then after fabricating a flycutter
and index latch for my lathe, I cut the splines in each end of the
shaft. Since I’d removed the pinion gear to disassemble the
old driveshaft from the gear housing, I had it available to test the
fit of my new splines. Once the splines were finished I matched the bottom end of the new
driveshaft with the original, marked the locations for the snaprings
that retain the pinion gear, and used the lathe to cut seats for
them. The keyway for the water pump impeller is just a flat spot on
the driveshaft.
It was simple to rough it out with a hacksaw and an angle grinder
and then to clean it up with a file.

Extending the column

Reassured that this whole exercise might actually work, I tackled
the extension fairing for the column. What I had available was 14-gauge
sheet steel (approximately .075 inch thick). I quickly determined
that
the curve at the leading edge of the column fairs back into a straight
line, so I could match it with just five sections of material as
shown at right: two curved for each side of the leading edge, two straight
for the trailing edges, and one flat piece for the back edge. I first obtained the outline of the required section by clamping
a sheet of heavy paper between the column and gear housing and tracing
around the joint. This also punched holes in the paper, providing locations
for the fasteners that connect the gear housing to the column. I translated
the tracing of the fairing cross section inward by the thickness of
my sheet stock, then cut templates from 1/2-inch plywood. Laying
the template on a flat surface, as shown in the top photo on the opposite
page, showed me where the trailing edge would begin. I marked this
location, then wrapped a strip of paper around the curve to the tip
of the profile, marking it to establish the length of sheet metal that
I would need to bend in order to form each side of the leading edge.
Later on, I used the templates to align the pieces of the extension
fairing while welding. Creating the curved sections for the leading edge of the fairing
involved lots of hammering with the sheet metal supported against cylindrical
objects of various diameters, such as an empty propane-torch tank and
a length of 2-inch iron pipe. I checked my progress frequently against
the plywood templates. I found that it worked best to create a curve
that was tighter than what I needed, then flatten it out progressively
by hammering against the anvil surface of a machinist’s vise.
(It took a while to form acceptable curves, but I got there eventually.) Once I had all the pieces of the fairing worked to their proper lengths,
I ground a chamfer of about 45 degrees on the outside of each edge
to be joined. This was to ensure good weld penetration of the entire
thickness of the sheet metal. This was important because I wanted
to build up a bead that I could later grind down flush with the outside
surface of the extension fairing. Assembling the pieces around my plywood templates, I tack-welded
them together with a MIG welder, then removed the forms. I completed
the
welds a bit at a time, allowing them to cool between passes in order
to minimize distortion of the sheet metal. I built each seam up into
a nice, heavy bead as shown in photo.

Once the shell of the extension was welded together, I used an angle
grinder to clean up the top and bottom edges, checking often with
a framing square to make sure the surfaces were parallel with reference
to the back edge of the fairing. I ground the edges until the height
was uniform and slightly more than six inches, then did the final
finish
with a large mill file across the entire top and bottom edges of
the shell to get the mating surfaces as straight and square as possible.
The holes that allow water to drain from the column after the motor
is hauled out were cut with a hacksaw and shaped with a file.

When I was satisfied with the fit of the shell against the gear housing
and the column, I fabricated alignment tabs from 1/8-inch by 1-inch
steel strap and welded them into the top and bottom of the fairing.
These provide lateral rigidity as well as ensuring that the extension
stays centered against the inside surfaces of the column and gear
housing.

I fabricated mounting flanges from 1/8-inch by 1-inch strap
to provide the connection points at the top and bottom of the fairing.
I first drilled the holes in them and then lined them up with the holes
in my templates and traced the outline that would become the edges
to be welded to the inside of the fairing shell. As the drawing above
shows, the flanges at the rear of the fairing are threaded for the
mounting bolts. Here I cheated: instead of spending a lot of time messing
around with taps to thread holes in the flanges themselves (in which
case they would have needed to be made of thicker material), I installed
a nut and bolt on each flange, with the nut on the inside face, then
I tack-welded the nuts to the flanges and removed the bolts. This provided
for a strong connection in a situation in which it’s impossible
to get a wrench on the nut. The bottom flange at the leading edge is constructed in much the
same way, but it uses a section of threaded rod to mirror the stud
on the
leading edge of the column. The upper flange merely has a plain hole
that the column stud passes through. It’s secured by a nut and
lockwasher from inside the extension fairing. (The original trailing-edge
mounting bolt was frozen; I was forced to drill it out. I elected to
install its replacement from the outside of the column, otherwise both
top flanges would have had plain holes.) Once the construction was complete, I ground the welds down flush
with the surface of the fairing, then polished the whole outside surface
with a 3M Scotch-Brite surface conditioning disc installed on an angle
grinder. This is the best way I’ve found so far to remove rust
and mill scale from steel components. It also left a very smooth, shiny
surface, which was important for the next step. Had I been thinking
ahead, I would have polished the inside surfaces of the fairing before
welding it together. Since I hadn’t polished the inside, I did
as much cleanup as I could afterward with wire brushes and a sand blaster.
Live and learn.

Powder coating

Because my materials were very susceptible to rust, it was important
to protect them. Epoxy-based or even enamel spray paint would probably
have been adequate, although getting good coverage on the inside
of the fairing would have been tricky. Luckily, I had a better alternative
available. Powder coating is a process that leaves metal parts with a smooth
protective layer that is harder and more durable than most paints,
covers irregular
surfaces more readily and uniformly, and is non-toxic to boot. The
process involves applying an electrostatic charge to a finely powdered
plastic that is then sprayed at low pressure over a grounded metal
part. The powder sticks to the metal surfaces just like dust to a
TV screen. Once it’s been coated, the part is baked in an electric oven
until the plastic melts, flows, and cures to a durable covering that
is resistant to abrasion and to most solvents. (The only thing I’ve
found to date that will attack powder coating is methylene chloride,
found in products such as spray-on gasket remover. Acetone dulls the
surface slightly; gasoline and oil run right off.) This was an industrial
process that required expensive equipment until a couple of years ago
when The Eastwood Company started selling a hobbyist’s powder-coating
package. Their basic HotCoat system sells for about $150. The nicest part of using the powder-coating process for this project
was that the charged powder was attracted to and covered every surface
of the fairing, inside and out, even the irregular surfaces of exposed
welds. To avoid fouling the threads, I installed bolts in the threaded
holes and masked off the trailing-edge stud with high-temperature fiberglass
tape (also from Eastwood) before coating everything with the shade
of powder I had on hand that came closest to matching the Eska’s
paint. Photos on Page 12 show the fairing after coating and the finished
powder-coated fairing after it was baked for 15 minutes at 400 degrees
F. I also powdercoated my new driveshaft after taping off the splines
and the surfaces that would bear on the bushings and seals. (Any
color would have done for the driveshaft; I happened to have black
in the
HotCoat gun at the time.) The final piece of the project was the extension for the cooling-water
tube. In this case I actually had to break down and go to the hardware
store to buy aluminum tubing that matched the 3/8-inch outside
diameter of the water tube, as well as vinyl hose with a 3/8-inch
inside diameter to join the extension to the original tube. (Since
I was there anyway, I also purchased stainless-steel cap screws, nuts,
and lockwashers.) I cut the ends of the new 6-inch extension to the
same angle as the end of the original water tube so they would fit
together flush, then smeared the outsides of the two aluminum pieces
with RTV silicone and joined them with a length of vinyl tubing as
shown in photo. (Epoxy might have been a better choice for this, but
so far the RTV seems to be working fine.)

Assembly is the reverse of removal

To reassemble the motor, I first coated all the bare metal surfaces
on the bottom end of the new driveshaft with a generous layer of
waterproof grease (meant for the wheel bearings of boat trailers) to
protect them
from rust, then reassembled the gear housing and driveshaft as shown
in photo.

With the motor supported upside down on an empty 5-gallon bucket,
I applied RTV silicone along the entire upper surface of the extension
fairing, then fitted the extension in place and bolted it on. The
trickiest
part of this operation was getting the nut started on the threads
of the stud inside the leading edge of the fairing. I found that a
telescoping
parts-retriever, a tool like a walkie-talkie antenna with a magnet
at the tip, was invaluable for this. Once the nut was finally engaged
with the threads of the stud, I tightened it with a socket on the
end of a long extension. With the motor still upside down, I coated the bottom of the extension
fairing with RTV, applied grease to the exposed metal at the top of
the driveshaft, and carefully lowered the gear housing assembly onto
the column until the driveshaft splines meshed with those in the clutch.
Working through the exhaust port and the small gap that remained between
the gear housing and the extension fairing, I used a long screwdriver
to jockey the end of the water tube into location in the water pump.
Once the driveshaft and water tube were started, I simply pushed the
gear housing down until it was seated on the extension fairing and
bolted it loosely into place. Before tightening the fasteners down
for good, I put the clutch selector in the “drive” position
and gave several pulls on the starting cord to make sure the driveshaft
wasn’t binding and in the hope that it would tend to align itself
by shifting the gear housing around slightly. The assembled result
is shown on the opposite page in bottom photo. After the RTV had cured, I refilled the gear housing with SAE 90
lubricant as specified in the Eska service manual and, using the time-honored
outboard-motor test stand, a sawhorse and a 55-gallon trash can full
of water, fired up my motor. With the gear selector in “neutral” I
was gratified to see that the clutch was now working properly. The
propeller remained motionless while exhaust racketed from the relief
port at the top of the column, sounding like a leafblower on steroids.
Once the motor warmed up and the idle settled down, I cautiously moved
the selector to “drive,” and . . . it worked!

Conclusions

I’ve been very pleased with this conversion’s performance
aboard Brushfire. With the motor mount in its lowest position, the
entire extension is underwater, giving the propeller plenty of bite,
and I can move forward in the boat without it becoming a menace to
low-flying birds. The tip of the gear housing’s fin is just
barely in the water with the motor mount in the topmost position. With
the motor rocked forward in its tilt bracket, everything is high and
dry. One odd side effect of the extension is that with the motor idling
and the gear selector in “neutral,” the exhaust resonates
inside the comparatively thin-walled extension fairing with a funny “bloop-bloop-bloop-bloop” note
that puts me in mind of The Secret Life of Walter Mitty.

If you don’t have a well-equipped metalworking facility in your
garage, you should be able to find a machine shop willing to fabricate
all or part of a similar shaft extension “kit.” Some
research in my area turned up two shops that were capable of the job,
one specializing in high-volume CNC production and not interested in
one-off jobs; the other a gear-making business that estimated $225
just to make the driveshaft. Though I haven’t had to take work
to a machine shop for nearly two decades, I find it hard to believe
that there’s nothing left but specialists.

Fabricating the driveshaft obviously requires some moderately specialized
equipment, but the operations involved are straightforward and shouldn’t
be too costly in terms of labor. (It took me about six hours all told,
but 80 percent of that was in building a flycutter.) If you don’t
have a welding outfit, any decent machine shop should be able to construct
the extension fairing as well. If you don’t know of a shop already,
talking to a few old-timers around your marina should turn up someone
who can do the job. Anyone who can cope with simple hand tools can
handle the fabrication of the cooling-water tube extension and the
final assembly. I’ve noticed that even a reconditioned long-shaft outboard starts
at $900; new ones are going for $1,500 or more. If you have an older
motor available, this project could be cost-effective even if you have
to farm out the actual fabrication work. (Not too long ago, I noticed
a 7-hp Eska identical to mine offered for $350 at my local marine exchange.
Now if I were to buy that and modify it I might be able to clear about
$500. Hmmm . . . )

Potential problems

Rust:

While I hadn’t noticed any signs of rust on
the exterior of the extension assembly, it still concerned
me that the whole thing is potentially susceptible to corrosion.
I’m relieved to report that, after four months and
about four-and-a-half hours of accumulated running time (including
two extended motor-only runs of an hour each), there was
no sign of a problem when I disassembled the extension to
take photos for this article. Brushfire sails in fresh water.
I would definitely go to the expense of using inherently
corrosion-resistant materials for saltwater operation, or
if the motor were semi-permanently installed in an outboard
well.

Sealing:

The through-the-prop exhaust system depends on a
good seal between the mating surfaces of the column, the
extension fairing, and the gear housing. The walls of the
column casting are about 1/8-inch thick, and the sealing
surface of the gear housing is a nice milled area that varies
from 1/4-inch to about 1/2-inch wide. The walls of the extension
fairing are roughly 1/16-inch thick, providing only minimal
sealing area. Almost immediately after I put the converted
motor into service I noticed bubbles of exhaust gases forcing
their way between these junctions. The RTV silicone obviously
wasn’t enough. I later made gaskets from 1/32-inch
automotive-gasket material and bedded them in hardening-type
gasket sealer. These worked for a while, but they eventually
started leaking also.

I’ve since welded lengths of 1/8-inch steel rod along
the inside of the extension fairing at the top and bottom,
making a generous bead that I ground down flat to provide
a wider sealing surface. I also filed the powder coat off
the mating surfaces. I suspect that the coating is so slick
that the sealants I’ve tried have not been able to
adhere to it very well. I have yet to put enough run-time
on the motor to tell whether this change will be effective.

Drain holes:

When I originally designed and built the extension,
I neglected to do anything about the original drain slots
at the bottom of the column’s leading edge. These
slots are right at the waterline, and when I first tried
the converted motor aboard Brushfire I noticed quite a bit
of exhaust escaping from them. My remedy wasn’t pretty,
but it does work: I threaded stainless-steel sheet metal
screws into two scraps of wood about 1/8-inch thick and,
with the extension fairing removed, filled the drain slots
with thickened epoxy, using the wood on the inside of the
column as backing. I tightened the screws down to hold the
wooden backing blocks in place while the epoxy cured, then
filed everything down flush with the mating surface of the
column. With the extension reassembled, the epoxy seals the
original drain holes. (The screw heads are visible in the
bottom photo on the opposite page, just above the top of
the extension fairing at the leading edge of the column.)

Shaft alignment and vibration:

I have no way to evaluate
this, since there’s so much incidental vibration when
the motor’s running. I’m reasonably confident
that the drive shaft itself is true, since I could check
that while I was machining it; I don’t know how accurately
it is aligned between the motor and gear housing but there’s
not a lot that I can think of to correct such a problem.
(I try to ignore the possibility, apart from making sure
I have fresh batteries in my hand-held VHF transceiver in
case the gear housing should fall off in mid-river and I
need to call for a tow.)

Resources

Bay Manufacturing
P.O. Box 1250
Milan, OH 44846
419-499-4602
http://www.baymfg.com

Certified
Parts Corporation
1111 W. Racine Street
P.O. Box 8468
Janesville, WI 53547-8468
608-752-9441
orders 800-356-0777
http://www.certifiedpartscorp.com

The
Eastwood Company
263 Shoemaker Road
Pottstown, PA 19464
800-345-1178
http://www.eastwoodco.com

Sea Scouts Ship 601
http://www.sss601.org/

Cory’s uncle taught him to sail when he was in high school. After 20 years, he’s
relearning those skills with the help of Brushfire, his 1975 San
Juan 24. Most of his sailing is done as a singlehander on the Columbia
River in Portland, Ore., but the right 30-something crewwoman could
change all that.