DIY Outboard Conversion

We use our E trolling motor on our 16' canoe (with outrigger )
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BTW our 18' bow rider is very long in the tooth. Nostalgia keeps me for taking it to the dump (wife's desire).
One man's junk is another man's treasure...
Chrysler OEM hull.
Ditto 140 hp
(A have a 10 up auxiliary motor. I do NOT want to use it for conversion.)
A few years ago I fried the original CDI, then a marine guy in Virginia showed me how to install a retro "Streetsmart" ignition - better than the original.
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BUT gas for a 2_stroke here in Canada is just too much and going up and up with carbon taxes.
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No need to get up and plane at over 40 mph anymore ( I am old).
Nobody wants a old 140 head. Up here even junk lower ends are not cheap, so...
I am wondering about using the 140 lower end as a test platform for a DIY unit.
(Note: last year I looked at a 10 hp conversion and he needed to add a bigger prop, because of slower RPM and torque. I already have a bigger prop, howbeit, running thru a heavy power end.)
If I started out with a 20 to 30 hp e-motor, there would be enough platform to perhaps add a second motor or go to a Leaf motor, IF the first proves successful.
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I was encouraged by Jamie from "Myth Busters" and his approx 30 up conversion (for actual professional use in the show).
Two caveats, he is smart and experienced AND money is not an object, though he was frugal/practical.
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My BIG QUESTION:
Am I being stupid thinking about the 140 platform ???

Dave
Some of the best cruising waterways here in the world - no palm trees.

 

Can you explain what is that you want to convert? Is it a 10 HP outboard, change to electric outboards or convert some 140 inboard?

 

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Gonzo:
First I want to sincerely thank you for responding.
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My tech buddies are always asking me to cut to the chase and skip the gab.
My first thoughts last year were to make a 10 hp equivalent e-motor, for 95 % of my fishing and just lower the 140, if weather requires a fast trip home. And that is still the plan gas or electric.
IF, our 10 hp proves too much to repair (I will know soon) THEN it would be a candidate to convert.
PLAN "B":
This is the reason I came on here for your expertise and advice...
We cannot spring for another even moderate engine, but if I decide it is not really necessary to use the 140, THEN, "How would it work as a lower unit for a larger e-motor" Yes the lower unit is heavy, but it's already on a hull that can hold it. Its bearings are heavier and it's prop is already larger for a lower RPM motor. Myth Busters used about a 35 hp e-motor (btw with jet lower end...
To the chase: could a 30 -40 e-motor work on that Chrysler 140 lower end ???

And thank you for being there.

Dave

45.9805 N, 81.9278 W

 

Obviously the electrical motor won't give the same performance as the 140 hp gasoline engine. But it could match part of that engine's power curve.
I'd try calculating your boats speed at that lesser power, from maybe the Crouch formula, or if you can find it, the power vs rpm of that engine. Whatever lesser speed you can reach with your electric will tell you what gearing you will need to use between the electric motor and the leg to reduce the electric's output rpm so that it corresponds to what the leg's prop needs to turn at to absorb that power.
It would make the job a lot easier if you got the lowest pitch prop you can find.

That's a long answer to say, it is certainly doable. Not necessarily practical because the internal friction losses on the large leg will be more that the losses on a small leg, given the same power input. Better to buy a dead outboard in the lower power range and work with that. Less losses.

 

I think by the time you invest in everything required to make a successful conversion, and part of that is it performing as you would like it to, the cost and hassle factor would be much higher than buying another gas outboard.

Most people make a conversion like this because they want to take on the challenge, or have a specific goal. It's not because they are choosing the quickest, easiest and most cost effective method to be out on the water fishing.

 

You should take into consideration the price of batteries, chargers, controllers, electric motor, cabling, etc. before starting on a conversion. If a tight budget is an issue, the cheapest solution is a used outboard in good condition.