Generator to electric motor outboard

Hi everyone,

I have an idea I'd like to put together in one of my speedboats. I want to replace an outboard engine motor unit with an electric motor, powered from an inboard mounted generator. Am I mad or is this perfectly possible?

Obviously I want to go stupidly quick - it's a speedboat - but I'm also after huge running times between tank fill ups. I have on an board fuel tank, so I'm also thinking of hooking that to the generator so that I can just keep going. Currently a 50hp outboard is the recommended unit for power, but that just drinks fuel - there must be a better way.....

Ideas anyone?

thanks.

 

Have you looked at available hardware.

Typical generators and motors are not high efficiency. At the cheap end of the spectrum you will lose about 15% each. At the high dollar end you might lose 8%.

So that means for the same shaft output, your primary engine will need to put out 1.2 to 1.4 times what an outboard engine would have to put out.

Then there is the extra weight.

Using an engine - generator with a remote motor make sense in some specialty applications.

However the downsides are extra cost, complexity and efficiency losses.

 

It can be made to work. However, it will use more fuel, be heavier and cost more. If you want to go stupidly fast and feeding a 50HP outboard is a problem, maybe high speed is beyond your budget.

 

To replace the 50 hp outboard you need a 40 KW generator, only available as a diesel, 5 times heavier than the outboard.
The extra losses have already been pointed out by other posters.

The answer to your question: YES, you're mad!

 

Talk to the bloke who was going to power his boat by hydro-electric turbine generation from the wake of the vessel. If he has it operating successfully, you are advised to proceed with his concept, otherwise not !

 

You could do it, won't be cheap though.

BLDC motor and controller, probably need less e motor power rating than gas due to its power delivery. Then lithium battery bank to smooth out your peak and average power consumption, then a small gas generator to keep the bats topped up.

Really though a 4 stroke ob is the better solution, and much cheaper than doing the e conversion in a way that actually works.

 

Good one.

 

Nope, there's not.... at high speed your cheap, simple and relatively lightweight gasoline outboard is by far the best option.

If you had said you wanted to go slow (4-6 knots) for prolonged periods then a combination of electric outboard, a battery+charger and a small generator makes some sense. Throw in a small solar panel to recharge the battery for free when you don't use the boat.