Simple Outboard Conversion

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Sep 21, 2010
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Hey Guys! First electric project I've finished (or at least come close to finishing) in awhile. Motor is an ME0709, 1:1 chain drive to the original lower unit shaft with the original splined coupler from the gas power head's crank. It will eventually be running at ~100V nominal and 70-80A, with performance very similar to the stock engine. I'll post some pictures and video of the boat running when we get it all buttoned up, mounted, and tested on the boat.

The controller will be the Hungarian eBay unit with a custom case and possibly water cooling, if necessary. Batteries are EIG LFP pouches in pre-configured modules
 
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Well it is looking pretty good so far. Would love to see more pics as you come along!

What outboard engine did you start out with?
 
How well did this work out for you? Reason I'm asking is I just moved onto a private lake that only allows electric motors. I'd love to put together and electric outboard for next summer!

Lately I've had my eye on a 14' boat that looks like the picture but currently has no engine. I'm thinking I don't want anything fast. It just needs to look cool and go 5-10MPH max.
 
CobraJet said:
How well did this work out for you? Reason I'm asking is I just moved onto a private lake that only allows electric motors. I'd love to put together and electric outboard for next summer!

Lately I've had my eye on a 14' boat that looks like the picture but currently has no engine. I'm thinking I don't want anything fast. It just needs to look cool and go 5-10MPH max.

Might be cheaper to buy a ready made electric outboard from China? Although building your own conversion might be more fun? It seems you'll need around 1000W-1200W to go 10MPH.
https://www.aliexpress.com/item/32713790916.html?spm=2114.12010612.8148356.47.e9a9287awP9OcS
If you want to do a conversion then a drive train package like this might be an idea:
https://www.aliexpress.com/item/32956364535.html?spm=a2g0s.8937460.0.0.67df2e0ejaQsWu
 
SlowCo said:
Might be cheaper to buy a ready made electric outboard from China? Although building your own conversion might be more fun? It seems you'll need around 1000W-1200W to go 10MPH.
https://www.aliexpress.com/item/32713790916.html?spm=2114.12010612.8148356.47.e9a9287awP9OcS
If you want to do a conversion then a drive train package like this might be an idea:
https://www.aliexpress.com/item/32956364535.html?spm=a2g0s.8937460.0.0.67df2e0ejaQsWu

Oh that is cool, I didn't know there were ready made electric outboard motors already available! I've looked at the more powerful electric trolling motors but those things are damned expensive! If I thought that 5 HP would do it I already have a really nice 4000 watt motor that I'd adapt, but I think that won't be quite enough.

I had a much smaller and lighter boat with a 5HP gas engine on it at one time. Even on it's good running days it would barely hit 5 MPH with only myself in it. I'm thinking that the boat I'm looking at is going to need a bit more OOooommph behind it to get any better speed.

I'm open to any other ideas though!
 
I'm not a boat person but it seems that the speed of a boat is mostly determined by the amount of water it has to displace and the shape of the hull. There are many YouTube video's where people experiment with electric outboard conversions. So it should be possible to guesstimate how much power you'll probably need to go more than 5MPH. I do think that a trolling motor style conversion where the motor and prop are under water will be most efficient. Or even an inboard set up if possible.
 
Oh that is just too cool, I'm glad you were successful with it! :bigthumb:

What were your final numbers on the power it required? ( running volts, amps, watts?)
 
coleasterling said:
.....

..... we're somewhere around 11hp out after losses. I limited both motor and battery current to 93A to be nice to the lower unit.

What HP was the outboard originally and what size prop is it swinging? Did you happen to get any RPM readings?

BTW, what do you think about those batteries? Where they up to your expectations?

The reason I'm asking all these questions is I just got an electric boat. It is currently running what I was told is a golf cart motor off of 4 X 6V deep cycle batteries. It's spinning a super tiny prop (maybe 6") at a ridiculously slow RPM (maybe 1000 RPM). Top speed so far is ~1.3 MPH!

I'm hoping to get something similar to the performance that you've exhibited. Although the lake we live on we're limited to 5MPH max and electric power only. I'm not thrilled about changing my entire drive train but eventually I think that I'll be bored with it if I don't!
 

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Looks like a nice setup begging for better batteries and more voltage!

It was originally 8hp at...5000? rpm. We're doing around 5100rpm measured flat out with an 7.5" two blade with what we think is a 6 pitch.

The batteries are great, just heavy and have a very low volumetric energy density.
 
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