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Converting to electric motor

Nov 14, 2008
Fantasia 35 Mark I Pt. Richmond, CA
I have a Fantasia 35 (Hull No. 11 - although I've never actually seen it). I am thinking about replacing the diesel (a 1987 Nanni 30) with an electric motor, battery bank (LiPO4), solar panels, wind generator, and auxiliary diesel generator. Has anyone made this conversion, how costly was it,how has it performed, problems, pitfalls, etc.
Ron Harben
S/V Puma Kai
Nov 8, 2007
Hunter 27_75-84 Sandusky Harbor Marina, Ohio
I haven't done it, but if you are considering it, think about using the motor as a generator while sailing. There are some suppliers of a propulsion system like that.

Personally, I end up asking why trade my main diesel for a generator engine and an electric motor? Diesel fuel is a great way to store energy under way.
Jun 6, 2006
currently boatless wishing Harrington Harbor North, MD
fuel to rotary motion
fuel to rotary motion to electricity to chemical storage to electricity to rotary motion.

One of these is more efficient and has fewer parts to malfunction. It would seem to be obvious which method of spinning the prop is less likely to have problems and provide greater range.
BTW your solar and wind are microscopic sources of energy compared the that diesel storage tank
May 24, 2004
CC 30 South Florida
I think a company in Russia can supply a small nuclear power plant to drive a boat electric motor for many years between refueling. Would be concerned about glowing in the dark.
Jul 20, 2005
Whitby 55 Kemah, Tx
Actually, generators a much more efficient engines then your typical motor. Generator motors are designed to run at 1 set RPM and therefore getting the most out of the engine and fuel. On top of that, you don't even need batteries with this setup but would need to run the generator at all times when motoring, where as if you have a battery bank for it, that bank would cover your typical motoring in and out of your dockage and the shore power can recharge the bank.

This is a system that some very expensive cat makers use as it is cheaper to have one generator and two electric engines then two diesel engines and performance is much better. Unlike combustion engines, electric engines provide 100% torque at all speeds.

I also like that the genset of the genset/electric combination can be used to charge the house bank when on anchor....maybe even while motoring if done right. I personally wish I went that route when I replaced my diesel engine. I could have freed up my lazarette that holds the genset already on the boat (not strong enough to push the boat).

The rest of what Bill says is true....more to break and you aren't going to recharge that bank with solar or wind.
May 24, 2004
CC 30 South Florida
My diesel engine already runs 98% of the time at one set RPM, at around 2,200 turns, and burns under 1/2 gallon of fuel an hour. Afraid that the generator engine capable of powering an adequate electric motor would have to be larger than the auxiliary diesel. Nice theories but let's talk reality. What voltage? Power rating of electric motor? Starting and Running Amp requirements? Size and weight of generator required? Fuel consumption of generator engine? Wiring size and protection? etc. If all these answers were to be positive I would think electric motors would be in wide use today and they are not.
Jan 22, 2008
Beneteau 323 Annapolis MD
IIRC, in recent years a company developed a "device" that runs as a motor, then the power train is put in neutral then the motor is a generator- maybe from the rotating the drive shaft/prop? Probably something I saw in Mechanics Illustrated?