I can't say because using the original engine's HP would be making the assumption that it was the optimal HP to begin with. Like others have posted, many boats are overpowered.
Oh, and 1HP = .75 kW, so 1000W = 1.3 HP
Frankly, unless one of our members has a similar sized boat to go by, you might have to do some testing or engineering. What you could do is tow the boat using a pound scale to log the force needed at various speeds and work forward from there.
--- In electricboats@
>
> Dan,
>
> So what size electric motor would you suggest to replace a 100hp engine in a power boat? (assuming that the engine was appropriately sized)
>
> Eric
>
> --- In electricboats@
> >
> > It's not so much a matter of efficiency, since horsepower is measured at the output shaft and any inefficiencies are already taken into account. Rather, it is a matter of the power curves. An ICE's HP is rated at WOT where it produces max HP, but torque is usually starting to drop. Plus, an electric motor's HP is rated at the point were it can run all day without overheating. The fact is, electric motors can be run at higher rpms, and therefore higher HP, for a short period of time. You can use this limited service factor for conditions where you want more HP, such as maneuvering or emergencies.
> >
> >
> >
> > --- In electricboats@
> > >
> > > You are correct. People will usually figure that an electric drive will be 2 to 3 times as effficient as an ICE engine in converting energy into thrust, due to less energy lost as heat. Therefore, a 100hp gas or diesel engine can usually be replaced with a 35-50hp motor with similar performance results. Unfortunately, a 50hp motor will draw at least 38kW under full power, which translates to 380A at 100V. So these kinds of power ratings require even higher voltages to keep the amperages reasonable. That doesn't even begin to address the problems of energy storage...
> > >
> > > Fair winds.
> > > Eric
> > > Marina del Rey
> > >
> > > --- In electricboats@
> > > >
> > > > I thought that I read that a 100 hp motor would be the same as a 200 hp gas engine?
> > > >
> > > > Sent from my iPhone
> > > >
> > > > On Apr 7, 2010, at 9:44 PM, "peoria_diver" <daredster@> wrote:
> > > >
> > > >
> > > > Denny,
> > > >
> > > > Following sugestions from this group, I did a little online shopping today. Powerboat hulls just don't seem like good candidates to me. Even small trawlers have engines in the 100HP range. I switched back to sailboats and found a couple of centerboard boats at 28'. I am still a little concerned about the stability. I'll have to give it some thought.
> > > >
> > > > -Red
> > > >
> > >
> >
>
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