I am about to start the process of re-powering my 35' Columbia with an electric drive from Propulsion Marine. I currently have a 27hp 3GM Yanmar and will be installing a 6.5KW system. Here is info based on Propulsion Marine's website FAQ' for gearing:
"Electric horsepower is equal to between 3 to 4 times that of diesel horsepower due to inherent power losses with an ICE (alternator load drag, transmission inefficiency, water pump, etc.) One horsepower equates to 746 watts and extrapolating it out we get one Kilowatt = 1.34 h.p. Our 6.5 KW motor consumes 8.71 h.p. Multiply that by 3.5 and you get 30.84 h.p. which is the diesel equivalent."
My boat displaces 13,900 lbs. and I have targeted my gearing/prop selection to give me 2 hours runtime @ 5.5kts with 80% DOD on AGM batteries. Dropping the speed to 3.5 kts. more than doubles my range.
The main issue is battery bank capacity. I am planning on installing 2 banks of either 4D or 8D's with a projected capacity or between 18.5 Kw hours and 22.5 Kw hours reserve depending on which batteries I go with.
I will be putting my motor up for sale shortly. It has approx 500 hours on it and is in excellent condition. Paint looks great and there is little to no rust. My wife is completely deaf in one ear and almost complete in the other so the decision to go electric has to do with noise reduction as anything. we need to be able to hear one another while under power and this seems like a solution for us.
Robert
--- In electricboats@yahoogroups.com, "GeoG" <GNHBus@...> wrote:
>
> Greetings to ALL,
>
> I had a very interesting conversation with a Westerbeke Distributor, 40 yr man, knows quite a bit about marine engines.
>
> I asked him if he could describe the differences regarding Torque, Thrust, Propellor Design, when comparing ICE & Electric Propulsion Systems for marine applications, and he could not.
>
> I want to decide between a 30hp ICE & an Electric Propulsion System for thrusting a 15,000 lb displacement hull at 6 knots for 4 hrs/day.
>
> Does anyone have a good understanding on this subject ?
>
> Best Regards
>
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