Electrify my boat?

by Jim Cochran
(San Carlos, Sonora, Mexico)

All gutted out, waiting for diesel-electric system

All gutted out, waiting for diesel-electric system

I have a 43 foot sailboat weighs about 11 tons. Want to make it diesel-electric! I have purchased a 13kw (continuous duty) diesel generator, but the rest of it??? Looking for ideas!

Hi, Jim!
Ideas, maybe not - but I do have a person for you.I was just talking to someone the other day in Florida who converts all sorts of vehicles to run on electricity; high-end sports cars, buses, trucks, boats, you name it. Quite a wide range of experience!
His name is Steve Clunn, and his website is Green Shed Conversions. You can find his contact information on his website.

Best of luck with your boat project, and keep us posted.


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Diesel > AC Generator > VFD > 3 Phase motors
by: Dave

Hi Dan Bentler, I have entry level knowledge of VFD's and the efficient power management and control they offer. I am looking for a ~28-33' yacht with no power train to retro fit with a single engine, a 3 phase generator to run a VFD and drive 2 or 3, 3-phase motors.

I would estimate a yacht of that length to weigh about 8,000 - 13,000lbs.

I see a lot of articles about using a "DC approach" and battery banks (In my view... very limited run time, HEAVY and need to be replaced - cost to power ratio, not good), I feel AC is definitely the way to go especially since that is the default form of energy coming from a rotational generator.

My interest in doing a retrofit using 3 phase motors in the propulsion system is that I suspect it would be a far more cost effective way to move a vessel through the water and with feedback capability for VFD learn/teach mode as apposed to running one or more large gas or diesel engines direct coupled to a prop. Also being able easily use multiple (electric) props off of a single generator reduces cavitation, improving efficiency.

My question is, do you agree? The cost of fueling a yacht of this size with a conventional direct coupled system has me thinking that I would spend more time budgeting for fuel costs than being out on the water.

Thanks for sound boarding with me!


by: Anonymous

I am very intrigued by the electric motor conversions yall are preposing. Would it be possible, if one understood the inherent limitations, to recharge your battery supply with a complimenting solar setup for such a high KW usage?

You mean, to have a solar array at home to recharge your boat's batteries? Yes indeed. To have a solar array on the boat that would supply all your energy needs? Not yet. There's not enough room on your boat for all the solar panels required, and they create drag and extra weight and whatnot and are atm just about 20% efficient at capturing solar energy.

However...I could see a permanent offshore floating island of solar panels, owned cooperatively maybe, where people could recharge their boats. Why not?

Marine electric propulsion
by: Dan Bentler

Diesel electric is a well proven way to go. Not only can you drive the boat with the generator but you also have plenty of power. I assume the alternator is 3 phase.

You will have to have a good idea of what your total load will be and ensure you do not run too much on the genset.

Well you can have the best of all worlds. The optimum would be twin screw using a pair of 5 Kw motors. Drive each with a VFD and you have variable speed, reversing etc etc.

OR you can have single 10 Kw and again drive with VFD and 3 phase motor. That will give you about 12 HP which may not sound like much but that equates to 24 HP in an engine. You may still be a little underpowered for a 43 foot but it is a sailboat and you are supposed to be sailing and not listening to that dang diesel banging away.

I live aboard a Newport 30 in Seattle so I know a few things about sailboats also,

I recommend 3 phase because you have no brushes commutator water problems (well a lot less than with DC motors).

I am an industrial electrician and learned the trade on submarines.

Dan Bentler

Boat power
by: Anonymous

13 kw is partway between 15 and 20 hp. Go 3 phase if possible for efficiency. The only serious constraint I see is max revolutions for your screw. The ac controllers are awesome. You can generally overspeed them by a factor of 2 (subtract 20% power for continuous running at this speed)

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