Electric Outboards. Comparisons???

[Peppermint]

How does one calculate how many watts of power or kp's of thrust, delivered by an electric outboard, adds up to a 2.5hp outboard. As I remember hp is a bit complex but roughly 746 watts is 1hp. Now that means that 2.5hp is 1865 watts.

Now clearly I'm missing something here because that seems like to many watts to me.

So can anyone tell me how big an electric outboard I need to get similar thrust to a 2.5hp petrol OB?

 

[pvb]

They don\'t make them that big...

Electric outboards tend to be rated according to thrust, often measured in pounds (as the US seems to be a major market for electric outboards). About 75 pounds thrust is equivalent to a 1hp motor. So to get the same thrust as a 2.5hp outboard, you'd be looking at nearly 200lbs. The biggest electric outboards only produce about 100lbs thrust, and these run on 36volts to keep current down to a manageable level.

 

[TrueBlue]

I don't think you can get an electric outboard with that sort of power output - 'cos the battery size would be horrendous.

I won't even start to discuss the battery capacity question, or whether you need 2.5Hp, or the energy / efficiency / conversion issues, or the fact that if one existed it would probably need 36/48/or even 96volt battery to run it.

I think you may be seduced by the little Min-Kota OB which can't do more than just tiddle along. I am reliably informed that's just what they're designed for - trolling through the water slowly and quietly spinning for fish, not planing along (!) from shore to ship.

 

[Evadne]

Re: Electric Outboards. Experience

I gave up trying to work out how many hp my electric o/b actually puts out, but a 24lb thrust one will push a dinghy (7' 6" praam) with two adults and their weekend luggage, faster than I can row in flat water. As you say 770W = 1hp, but that means a 1hp motor is drawing over 60A, and I find it hard to believe that mine does. Probably more like 10A. I'd prefer a more powerful one, 36lb or 48lb to be able to make more way in strong winds (an F6 or more on the nose will all but stop her). I'd have said 48lb gives a similar performance to a 1hp petrol jobbie, from a practical point of view. The many advantages outweigh the one disadvantage in my case. i.e. lack of power vs:
1. No petrol
2. Easy starting
3. Quietness
4. My engineophobic wife will happily use it
5. No petrol

 

[Peppermint]

Re: Electric Outboards. Experience

Thank you. Thats what I needed.