Electric conversion for Hunter sailboat

Bill Roosa · Jul 30, 2016

Is it possible? yes. In your case it might even be practical. however, the calculation for the battery bank needed for a 1 HP motor go like this;
1 HP = 746 watts. At 12 volts that is (P/V=I) 746/12 = 62 amps. If you run the motor twice getting in and out of the marina for 15 minutes (0.5 hours) that is 62*0.5= 31 Amp-hours (Ah).
The unfortunate part is you will probably need something like 10+ HP to account for wind, current etc. so what you need is 310 Ah. and you don't want to discharge your bank below 50% so 620 Ah just to get in and out of port. That gives you some reserve (take the bank below 50%) but I'd not plan on using that except an emergency.
If you plan to sail to another location and us the motor for 15 minutes getting in and out of that port then return to you home port (all without charging the bank) you end up with a 1240 Ah bank........
So you need to determine what HP you need and consider what the next owner is going to think about only having a 0.5 hour motor.....
good luck

Johnb · Jul 30, 2016

What Bill has said is that electric power is miserably lacking in capability as things stand. If you really can't afford/don't want to spend for a new diesel, you would be better off going the outboard route. That would be cheaper and way more capable than electric.
There was a long thread previously on this topic. Pretty much beat it to death

http://forums.sailboatowners.com/index.php?threads/replacing-diesel-with-electric-engine.165653/

whatfiero · Jul 31, 2016

On a lake a fresh water environment I'd be curious at possible gas conversion I realise it's a back ward's conversion but a dependable 12 hp 2 cylinder Honda v twin from northern tool cost like $600 on sale it's like 400 lbs lighter than the yanmar electric start the only challenge would be adapting shaft to existing transmission but possible a good machine shop could make an adapter plate and shaft coupling to do then custom motor mounts reconfige wiring and done small altnator so no recharging on hook

flynhi4u · Aug 1, 2016

whatfiero said:
On a lake a fresh water environment I'd be curious at possible gas conversion I realise it's a back ward's conversion but a dependable 12 hp 2 cylinder Honda v twin from northern tool cost like $600 on sale it's like 400 lbs lighter than the yanmar electric start the only challenge would be adapting shaft to existing transmission but possible a good machine shop could make an adapter plate and shaft coupling to do then custom motor mounts reconfige wiring and done small altnator so no recharging on hook

That is an interesting thought. The Honda would be air cooled so you would have to cap the water inlets and plumb in air ducts for cooling air and then a way to get the heated air out of the engine compartment.
A good outboard would be a lot less hassle though.

Sam

whatfiero · Aug 1, 2016

Flynhigh4u I just added a 4" duct and blower fan to do that with my yanmar diesel to pull some of that heat out the dog house in summer so that part possible the exhaust would be the next challange

flynhi4u · Aug 1, 2016

Oh it is defiantly doable, would just require some patience and thought. You would still have the non marine carb to deal with. Not sure how well the ins companies would like that.

Sam

Jackdaw · Aug 1, 2016

http://www.thunderstruck-ev.com/

flynhi4u · Aug 1, 2016

Jackdaw said:
http://www.thunderstruck-ev.com/

Interesting site. The price is certainly attractive till you factor in the battery cost. I would think for someone who sails a small inland lake with wind that can be counted on more often than not this would be a viable and "green" alternative. Not sure how well it would work for "cruisers" but I would be interested in hearing from an actual user.

Sam

uncledom · Aug 1, 2016

Hunter made a hybrid electric boat. I think it was a 32'. I think Elco makes electric boat propulsion systems. They don't run them at 12V.

Jackdaw · Aug 1, 2016

flynhi4u said:
Interesting site. The price is certainly attractive till you factor in the battery cost. I would think for someone who sails a small inland lake with wind that can be counted on more often than not this would be a viable and "green" alternative. Not sure how well it would work for "cruisers" but I would be interested in hearing from an actual user.

Sam

Correct, The OP posted this "the boat is on a large lake in Georgia and the motor is only used to get in and out of the marina, usually less than fifteen minutes." and that is the perfect use case.

It looks like a well engineered system for a particular type of user. I'm sure it would come in less, but its not designed to be an el-cheepo way to replace your dead diesel.

timangiel · Aug 21, 2016

Bill Roosa said:
Is it possible? yes. In your case it might even be practical. however, the calculation for the battery bank needed for a 1 HP motor go like this;
1 HP = 746 watts. At 12 volts that is (P/V=I) 746/12 = 62 amps. If you run the motor twice getting in and out of the marina for 15 minutes (0.5 hours) that is 62*0.5= 31 Amp-hours (Ah).
The unfortunate part is you will probably need something like 10+ HP to account for wind, current etc. so what you need is 310 Ah. and you don't want to discharge your bank below 50% so 620 Ah just to get in and out of port. That gives you some reserve (take the bank below 50%) but I'd not plan on using that except an emergency.
If you plan to sail to another location and us the motor for 15 minutes getting in and out of that port then return to you home port (all without charging the bank) you end up with a 1240 Ah bank........
So you need to determine what HP you need and consider what the next owner is going to think about only having a 0.5 hour motor.....
good luck

If you actually do an electric conversion you would not use a 12v motor.

seadaddler · Aug 22, 2016

Hunter did have a electric H-36 and did see it at the Miami boat show a few years ago and
was impressive for sure with solar panels on the bimini and also a I think a Gen backup option.
Nick