Electric conversion journal
We own 50% of a 1973 Coronado 32 MkII sailboat. The “Cabernet” is a well cared for, spacious, 32 foot
cruiser. We are the third owners since the boat was new, and bought the boat, with our partners, in 2005.
In the fall of 2008 we started having engine problems and eventually discovered rusted pin holes in the bottom
of the steel gas tank (original, 36 years old), that were letting rainwater into the tank. We removed the gas tank
and, while waiting for a custom tank to be built, ran the engine using a 5 gallon outboard tank temporarily
secured in the rear lazarette.
The original Palmer 60 four cylinder gas engine (the same as a FarmAll tractor engine) generally ran very well,
but while trying to fix the gas tank problem we messed with the carburetor, etc., so idling had become rough.
We worked with other mechanically experienced members of our sailing association, but the engine was still
When we did the 2009 annual oil and filter change, we suddenly began having severe oil leakage after an hour
or so of run time. Fortunately all the oil was contained in the engine bilge and we were able to remove it and
add more oil to the engine before there was any pollution or engine damage. After searching high and low for
the source of this delayed, intermittent leak, we suspect the crankcase is being pressurized for some reason and
is blowing oil out the rear crankshaft seal. This requires the engine be removed to repair.
As an electric vehicle enthusiast, I wondered if we could convert the sailboat to reliable, silent, electric drive. I
researched the web and found Electric Yacht (www.electricyacht.com). We generally need only a short period
of engine run time, to get away from the dock before sailing, and another short period to get back into the dock
after dropping sails. Sometimes we motor for longer periods if we are on an extended trip or the wind dies
when we are quite a ways from the dock. Two to four hours of motor time usually gets us where we need to go,
but for extended trips up 55 mile long Lake Chelan, up to six hours of motor time a day may be needed. Based
on discussions with Electric Yacht, we expect to use about 40 amps at 5 knots cruising speed. If we discharge
batteries to only 50% state of charge (for longer battery life), we would need about 200 amp hours minimum
battery capacity for two hour motoring range. For extended motoring, we’ll need a generator to supplement
battery capacity. A 2,000 watt Honda EU generator would fit into the rear lazarette and provide 15 amps of
power, the same as the shore power outlet at our boat partner’s dock.
After talking it over with our boat partners, we decided to convert the sailboat to electric drive. We put the
custom gas tank order on hold, and I ordered a conversion kit from Electric Yacht. Scott, at Electric Yacht, and
I exchanged a few of e-mails to nail down design issues, and we received a 130i conversion kit about Sept 1st,
2009. Having done vehicle conversions, I was impressed with the compact, well constructed, Electric Yacht
10/8/09: This is the first day we’ve had to work on the electric conversion. I intended to just get the engine
ready to remove, but our boat partner, Don, was ready to “go for it”.
I disconnected the temporary gas tank and fuel pump; drained the fuel lines, and removed the fuel/water
separator filter. I closed the sea cock for the engine fresh water intake and disconnected the fresh water lines to
the engine. I turned the battery selection switch to “off”, and disconnected the negative lead from both batteries.
I then removed the electrical wires from the engine – labeling each one to show where it was connected. I also
removed the throttle, choke, and V drive shifter connections. I secured the prop shaft with a collar sent in the
kit by Electric Yacht, so it cannot slide out through the packing nut and hull. I then removed the 3 bolts from
the prop shaft/V drive coupler.
Motor ready to hoist.
While I worked on the engine, Don rigged the boom to serve as a hoist. He reinforced the boom by attaching
the main halyard to the topping lift connection at the aft end, and tensioning both lines. He rigged a heavy
nylon tow strap to the boom to attach the small chain hoist we had borrowed.
Meanwhile, I removed the lag screws that secured the motor mounts to the engine bay rails. But the rear, port
side, motor mount was rusted so badly that the lag screws could not be removed. After also failing to remove
the motor mount bolt with a 1/2″ cordless impact driver (the nut and bolt were rusted and the whole rubber
assembly just turned slowly), I finally used a cordless angle grinder to cut the motor mount bolt in half, freeing
We then attached the chain hoist to the engine lifting loop and hoisted the engine. With help from my wife,
Anne, we were able to get the engine out through the companionway and sat it on a 2 x 10 support in the
cockpit while we shortened our lifting chain.
Motor hoisted out into the cockpit.
We then hoisted the motor as high as possible and swung the boom out over the dock and lowered the engine
down onto the dock.
Engine lowered onto the dock.
There’s a ton of space left in the engine bay for the electric motor and batteries. (3 hours today)
Empty, still dirty, engine bay. Note remaining motor mount I had to cut off in upper right of photo.
10/11/09: Sailing association members answered the call for help getting the gas engine up a long flight of
stairs from the dock. Six people carried the engine to the base of the stairs, where it was strapped to a hand cart
with “stair climber” rubber belts on the rear. A 4′ long, 3/4″ rebar anchor was driven in at the top of the stairs,
and the chain hoist and a come-along were used to winch the hand cart up the stairs. Then the cart was wheeled
through a garage to my utility trailer in the driveway. We’ll keep the engine until we’re sure the electric
conversion meets our needs.
Winching the engine, steadied with straps, up the stairs, being sure no one was below in the “fall zone”.
The next step was to test fit the electric motor to the prop shaft to see if the companionway stairs would clear
At 70 lbs, the electric motor was much easier to get onto the boat.
Before test fitting the motor, we placed a 2 x 2 straight edge across the engine rails and measured the distance to
the top of the prop shaft. We will need to duplicate this distance when the motor is mounted, to avoid binding
and excessive wear on the prop shaft bearing and packing. We used the main halyard, extended by a dock line,
to lower the motor into place and provide support while the coupler was attached to the prop shaft.
Supporting motor with an extended halyard while fitting it to the prop shaft.
We then blocked the motor in place to check clearances.
It was obvious that the motor controller extended too far forward for the companionway steps to clear.
We then checked motor mount placement.
The motor mount will need to be modified, or a custom mount made, to secure the motor to the engine bay
floor. The motor is too far forward to secure it to the original engine rails.
I crawled into the engine bay with a flashlight and had Don put the companion way steps in place to check for
clearance. We’ll remove the motor controller from the motor and mount it on the engine bay wall to move the
companionway steps as far aft as possible. It looks like we’ll also have to make a two inch extension for the top
step, and place a cleat forward on the floor, to have the steps clear the motor.
Ready to check companion way step clearances from inside the engine bay.
One way to avoid modifying the electric motor would be to use the original V drive. This would place the
electric motor further aft, allow use of the original engine rails for mounting, and avoid modifying the
companion way stairs to fit over the motor.
The original V drive changed output shaft direction to allow mounting the gas engine aft of the prop shaft.
However, after looking over the V drive, I realized it is heavy (about 50 lbs), is water cooled (which means it
generates heat while operating, which means it’s inefficient), and uses oil which would need to be changed
annually. These are all issues I want to avoid with the electric conversion. So we will move ahead to mount the
motor controller elsewhere, and modify the companionway steps to clear the motor. (2 hrs today.)
10/18/09: I removed the throttle cable, choke cable, and shifter cable. I removed the gas line and 5 gallon
temporary gas tank. I cleaned the engine bay, but it still needs more cleaning. I taped up all the wire terminals
in the engine bay to avoid any unwanted connections, then reconnected the starboard 12v battery. The bilge
pump now works (important!) and I left it on, as usual. The battery is being kept charged by shore power.
I measured the engine bay and drew up a battery plan when I got home. Eight 8G31 batteries (216 amp hours at
48v) will fit, in two rows of 3 end to end, with a row of two end to end in the middle. I’ll cut a 3/4″ plywood
floor to span, and screw to, the old engine rails, aft of the electric motor, to clamp the batteries to.
I also took the port 12v battery out, since we’ll only need one “house” battery. The house battery will be kept
charged with shore power or the generator on long trips. (2 hrs)
10/28/09: We received the batteries (eight MK 8G31, sealed, gel, $1,900), 48v battery charger (Interactor
ICS48/20, $400), and generator (Honda EU2000i, $999). After looking over the battery charger and generator
specs (more detailed than the info I looked at before ordering), it looks like they will work well together. I had
to call the manufacturer to get instructions for setting the battery charger internal DIP switches for gel batteries.
I read through the generator manual, added oil and gas, and fired it up. Works great. (2 hrs.)
11/4/09: Cleaned the engine bay thoroughly – taped unused wires up out of the way, removed the bilge pump
and relocated it behind the engine bay after removing the water muffler located there. I moved the suction
tubing for the bilge pump and rerouted it under the deck and around the engine bay. So the engine bay is as
empty as it can get and almost as clean as possible.
Empty and cleaned engine bay.
I test fit the 3/4″ plywood over the engine rails and marked how I’d like to set the batteries on it, using a foam
board battery model I made. So I can be sure how tall they are, etc. Looks like I’ll have room to also mount the
battery charger on the plywood.
I had noticed that when I turned the prop shaft by hand that the motor wobbled a little. I don’t think the prop
shaft is not bent, since we’ve never had any vibration issues with it before. I took the controller and motor off
the motor mount assembly, to lighten it up as much as possible. Then removed the shaft coupler and checked
that there was no debris or burrs inside to misalign the connection. I reconnected the coupler and still see a
small amount of wobble.
I studied the motor mount attachment and realized I could use the mount provided by Electric Yacht by
extending the existing engine rails forward. I think two Uni-Rac solar rail mounts will work and give lots of
flexibility for adjustments.
I also test fit the generator in the rear lazarette. It fits fine. I removed the engine bay blower exhaust tubing
from the engine bay to the blower, which is mounted just under the rear deck at the blower outlet. Running the
blower will now vent the engine bay, where the vent inlet tube comes in, and all the lazarettes. This should vent
the generator exhaust and heat.
I didn’t have wire with me to extend the bilge pump wiring, so will return tomorrow and get it rewired. (4 hrs)
11/5/09: Returned and wired the bilge pump, and also winterized the domestic water system with RV
antifreeze. I brought along two 24″ Uni-Rac solar mounting rails and they will work great for extending the
existing motor mount forward to mount the electric motor.
Motor mount using Uni-Rac solar rails.
11/8/09: I worked on fabricating the battery platform in my garage. I used 3/4″ exterior plywood and 3/4″
aluminum angle around the edge to keep the batteries from sliding around. I also used wood spacers between
the batteries to keep them from knocking around when we’re sailing and heeled over. The battery charger fit
perfectly in the space left. Alright! We’ll also use webbing from side to side over each set of batteries to insure
they don’t move around when heeling.
I made cables for the battery series and parallel connections, and wired the battery charger (which will have a
fuse on the positive lead when it’s wired on the boat) to the “most positive” and “most negative” terminals at
opposite ends of the battery bank. It worked out that these are at the forward end of the battery bank, where
they are easily accessible.
Battery platform and charger wired for testing.
I tested the battery charger, using a Kill-A-Watt meter and a wall outlet. It draws 12.5 amps. I then tested the
battery charger plugged into the generator. The generator is rated at 13.5 amps continuous, 16.6 amps for a
short duration. The generator handled the charger load OK. (3 hrs)
Generator for extended motoring range and recharging without shore power.
11/15/09: I finished mounting the electric motor mount. I lag screwed the Uni-Rac solar rails to the side of the
original motor mounts. They extend forward to mount the electric motor. The motor mount feels solid and the
prop shaft no longer wobbles when I turn it by hand. I measured the distance from the 2×2 used before the
engine was removed and confirmed the prop shaft is in the exact same location.
Completed motor mount.
I also installed an outlet and cord from the rear wall of the cockpit into the rear lazarette, to allow the shore
power cord adapter to plug into the generator. This provides a simple, fool proof, “transfer switch” to provide
AC power from either shore power or the generator, without both ever being connected at the same time.
Generator outlet (gray) to allow the shore power cord adapter to plug into the generator.
Inside the rear lazarette showing the new generator outlet and cord that will plug into the generator.
When I got home I worked on some 2″ nylon webbing that Don had to use for straps across the batteries and to
hold the generator down. (2 hrs)
11/16/09: I fabricated nylon strap hold downs and treated the plywood battery platform with water proofing.
Anne will sew the nylon straps to buckles and we’ll be ready to install the batteries. (1 hr)
11/17/09: Don and I installed the batteries. First we placed the plywood battery platform in the engine bay and
checked clearances again using the foam board battery model.
Battery platform in place and foam board battery model testing clearances.
Then I screwed the platform to the engine rails and we placed the batteries and strapped them down. (1 hr)
Batteries and charger installed.
12/2/09: I wired the battery bank, installed the main fuse and battery switch, and figured out where to mount
the motor controller on the engine bay wall. I used a cheap foam backpacking sleeping pad to lay over the
batteries so I could lay on them to make connections in the rear, and to prevent shorts if I dropped a tool. I also
removed the old shifter/throttle and decided where to mount the new electric shifter/throttle. It was about 30°F,
so I quit when I got cold. (2 hrs)
12/3/09: I finished wiring the main fuse and battery switch, mounted the controller (with the fan sticking
through a hole in the engine bay wall to the space under the galley sink, and nuts to hold the controller off the
wall 1/4″ for cooling) and wired it.
Controller and master battery switch mounted on engine bay wall.
Main battery fuse, with 30 amp in-line fuse for battery charger also visible, and unused wires from the gas
engine stowed out of the way.
I then temporarily connected the battery monitor and throttle cables to the controller and tried running the
system. It works! Yahoo!
But, the motor wobbles, so the shaft is not aligned properly. I called my boat partner, Don, and he came to see
and help. He disconnected the shaft coupler and we ran the motor again. No wobbles. So we’ll adjust the
coupler and motor mount alignment tomorrow to try to fix the wobble. We’ll remove the electric motor for
easier access to the shaft coupler and to make it easier to adjust alignment without the weight of the motor to
Don also helped me determine if the throttle was operating correctly in forward and reverse. It wasn’t, so we
dialed the “power” knob on the motor controller through center to change motor direction, as specified in the
Electric Yacht directions.
I mounted the throttle in the same hole as the original throttle/shifter, with another hole added for the key
switch. I had to shave the corner off the port lazarette hatch so it would close fully. The lazarette hatch cannot
be opened or closed if the throttle is in reverse. We’ll have to watch out for that. It was not possible to mount
the throttle farther forward to avoid the hatch because of a bulkhead behind the cockpit wall. We still need to
patch or cover the old holes for the choke and starter button.
Throttle mounted in same location as original throttle/shifter. White tape covers holes from choke and ignition.
I mounted the battery monitor on the port bulkhead near other instruments, where it is readily visible to the tiller
person. The display is large and easy to read. (4 hrs today.)
Battery monitor surface mounted on bulkhead.
12/4/09: I mounted the cable from the battery monitor to the inside of the bulkhead and down to the engine bay.
I also put a small bead of clear marine sealer/adhesive around the upper edge and sides of the battery monitor to
keep moisture out of the bulkhead hole. I left the bottom open to let condensation out. I relocated the main
battery fuse so the cable to the battery switch worked better and was no longer dangling in mid air. I measured
the battery charger and realized that if I removed the handle from the top, it would fit laying on it’s back, with
the on/off switch accessible and state of charge indicator lights visible. Worked great.
I then removed the electric motor and worked on aligning the prop shaft with the motor mount shaft. After
adjusting the motor mount upward, it looked like everything lined up well. I reassembled the motor to the
mount and tested it, but it still wobbles, although perhaps less. In the process the brass “B” electrical terminal
post on the motor snapped in two! Agh! I don’t think I torqued on it that hard. I was able to use the stub left to
carefully attach the power cable, but I’ll contact Electric Yacht to see about a permanent fix.
Jury rigged cable connection on the motor “B” post.
Here’s how the engine bay looks now.
I reread the Electric Yacht installation manual. We’re getting close to being ready for a shake down cruise. I’d
like to get the companion way stairs reinstalled first. (2 hrs)
12/5/09: I hard wired the 48v battery charger to the AC inlet. I had to extend the charger AC cord about 2 feet.
I then tested the charger and everything worked fine connected to shore power. I also installed the Honda
EU2000i generator, with a hold down strap, and tested it by plugging the shore power adapter cord into the
generator outlet I had installed earlier. The generator worked fine too, not too noisy and the original blower fan
seemed to clear the lazarette of fumes and heat.
The motor alignment and companion way stairs are all that remain, but it was cold so I called it a day. (1.5 hrs)
The Honda generator in the rear lazarette, with hold down strap attached to the floor board, and cord plugged in
for the generator outlet on the bulkhead to the cockpit.
12/13/09: It’s been very cold so I haven’t been working on the boat. Electric Yacht is sending a beefier set of L
brackets for the motor mount, as well as a replacement B post for the motor connection. Scott related that the
torque spec on the motor post is 65 inch pounds, which isn’t much, but then it’s a brass fitting. Well, I’m sure I
exceeded that, so will have to be more careful.
12/16/09: Received the new L brackets from Electric Yacht but it will be a few days before I can get to the boat
to try them. The replacement motor B post is still on the way. Also made a couple small metal “S” shaped
pieces to allow mounting the companion way stairs an inch and 3/4 further forward to clear the electric motor
mount. (1/2 hr)
12/21/09: Installed the new L bracket motor mounts, carefully aligning the shafts. But there is still a wobble.
And, I installed the shaft coupler too close to the motor mount, so it rubs on the grease fitting. I’ll have to do it
all over again. But I’m cold, so headed home. (1 hr)
12/23/09: Realigned the shafts, again, moving the coupler 1/4″ aft to clear the grease fitting. I also took the
shaft key out of the motor mount shaft, to make sure it was seated properly. It looks perfect, but there is still a
slight wobble. Agh! I also installed the metal “S” brackets, and a wooden spacer, to allow the companion way
stairs to be moved forward to clear the motor mount. But the stairs touch the motor mount so it transmits sound
and makes noise from the motor mount wobble.
Then we (me, Anne, Don, and Don’s wife, Jane) took Cabernet out for a shake down cruise! We followed the
Commissioning checklist in the Electric Yacht manual and determined that we could probably use less reduction
between the motor and prop shaft. At 3.5 knots (on the knot meter) we were pulling 51 amps. Slower than
hoped. Amps at max throttle was 68 at a little below 4 knots, and we’d like to see 100 amps or more at max
throttle without hitting “motor limit” (ML) on the battery monitor. So we will reduce the reduction ratio, load
the motor more, and hopefully get more speed. I e-mailed Electric Yacht and requested a couple larger sized
motor shaft pulleys to try.
I also noticed motor static on the VHF radio. I didn’t take time to play with the squelch to see if that eliminates
it. I’ll ask Electric Yacht about that too.
We also ran the generator and plugged into it. As expected, it provided about 20 amps of power to the battery
bank. In addition, it also ran the 12v charger and AC accessories we had on. This is great. We did have some
fumes in the engine bay area. I will enclose the generator area and run the fresh air inlet hose to it, so the
blower fan will exhaust only the small generator compartment.
It was cold, in the 20s, and mostly sunny with very light winds, so we didn’t motor long. But it was great to be
out on the water, using quiet electric power! (3 hrs)
On the shake down cruise. 51 amps at 3.5 knots. Note the large, easily readable, Battery Monitor display.
1/7/10: I received two larger motor pulleys from Electric Yacht a couple days ago and Don and I tried them
today. I installed the largest one first and we hit motor limit, “ML”, on the battery monitor display. I then
changed to the medium pulley and we hit 106 amps at maximum power/maximum throttle, and 5.1 knots speed
on the GPS (4.5 on the knot meter.) I “scaled” the power knob, as directed in the instructions, and throttled
back to 50 amps and we cruised at 4.3 knots. This is exactly what I had hoped for! We’ll have 2+ hours of
cruising range and stay at or above 50% state of charge. Perfect!
I added one of two ferrite rings Electric Yacht sent to the VHF radio power cable. It reduced the motor static
noise some, but there is still a serious whine that changes frequency with motor speed on both the fixed VHF
and handheld VHF. Scott at Electric Yacht said to try 3 or 4 loops of the power cable through the ring.
I also loosened the prop shaft packing nut to get at least one drop per minute. Scott said a tight packing nut
could reduce performance.
I looked carefully at the prop shaft coupler and it appears it’s still slightly out of alignment. Man, it’s harder
than I expected to get things lined up. I’ll keep at it.
It was great to motor quietly, hearing very little motor sound, and mostly hearing just the lap of the water on the
hull. Coming back into the dock we could throttle back to a slow drift with perfect throttle control. Awesome!
At the dock we plugged into shore power and I noticed the 48v battery charger was not working properly (no
charging LEDs lit). A quick inspection revealed the 30 amp fuse on the positive lead to the battery pack had
melted and blown. Yikes! I replaced the fuse with a 20 amp DC circuit breaker I had with me, and it tripped
too. I used a clamp on amp meter and found that the “20 amp charger” was putting out up to 32 amps into the
batteries! I can’t complain about the higher charging rate, but I’ll have to adjust for it. I changed to a 60 amp
breaker I had (still protects the 6 AWG wire) and everything worked fine.
Still some fine tuning to do, but we’re set for a longer cruise, 12 miles down lake, next weekend to display the
boat, with Christmas lights over the mast, at the local WinterFest Fire and Ice celebration. I’m very excited and
pleased with the electric propulsion system!
1/17/10: This weekend was the real test of the electric propulsion system. Yesterday, we motored 12 miles
down lake (no wind). We left our dock at 10 am and motored at 50 amps, about 4.5 knots on the GPS. 2 1/2
hours later we docked at Chelan with 50% battery capacity left. Perfect! We plugged the boat in to charge. At
our electric rates, it takes less than 30 cents of electricity to recharge the battery bank.
We returned at 4 pm. I reinstalled the bilge pump I removed yesterday, after cleaning debris out of the one way
valves, and insured it was working. I also added a grooved board to the cabin sole (screwed to the wooden
bilge cover) for the companionway steps to sit into, about 2″ forward from their original position. This allows
the steps to clear the electric motor and prevents the steps from sliding forward when someone steps on them.
It got dark about 4:30 pm and about 5 pm guests began to arrive. We had eight people on board when we
motored out from the dock at 5:30, with Christmas lights illuminated over the mast from bow to stern. Our
companion sailboat, a 30′ Catalina, warmed up her diesel engine and gassed us out, while we waited. Both
boats then motored out to watch the Chelan WinterFest, Fire and Ice festivities – a polar bear splash, bonfire of
Christmas trees, and fireworks. Spectacular! And enjoyed in nearly silent, oderless, electric drive. We could
talk quietly and hear our companion sailboat occupants talking. But they had to idle the diesel to hear us.
After the fireworks, we motored to a public dock at the foot of the main street in town and walked a half block
to a restaurant for dinner, leaving the Christmas lights over the mast lit. Then we returned and motored a mile
back to the dock for the night.
On Sunday morning we scooped an inch of new, wet, snow off the boat and prepared to motor back up lake to
our dock. I motored past the dock for some photo ops, then we headed up lake (again, no wind), arriving 2 1/2
hours later. The last half hour it started to rain, so we advanced the throttle to 75 amps, 5 knots, to get to our
dock sooner. Everything worked great and we enjoyed a quiet, odor free, trouble free, cruise.
The Cabernet cruising under electric power! Fair winds and following seas!
Summer 2010: None of our efforts to eliminate the radio interference on the marine VHF radio worked. The
static from the motor is also on marine VHF portable radios. After discussion with Electric Yacht, we upgraded
the motor to a 180i brushless motor and no longer have any static! :)