This Electric Outboard Conversion Makes For A Quiet Day On The Water

Nothing beats a day on the lake in a little boat with an outboard motor putt-putting along behind you. It’s great fun, if perhaps a little noisy with all that putting going on. And maybe that oily sheen on the water in your wake is not so nice. it could be that the fish are a little annoyed with your putting, too. Come to think of it, outboard motors are a bit of a problem.

Fortunately there’s a better way, like converting an old outboard motor to electric. It comes to us by way of [Anton], who happened upon the perfect donor platform — a 5-hp outboard by Crescent, sporting a glorious 1970s color scheme and a motor housing shell perfect for modding. He started by ripping the old engine and drivetrain out of the housing to make room for the BLDC motor and its driver. The motor was a project in itself; [Anton] rewound the original stator with much thicker wire and changed the coil configuration to milk as much torque as possible out of it. What started as a 180-kv motor ended up at 77 kv with much more copper and new Hall sensors for the controller. He also put a ton of effort into waterproofing the motor with epoxy resin. With a 3D-printed prop and a streamlined fairing, the new motor looks quite at home on the outboard. In fact, the whole thing barely looks customized at all — the speed control is even right on the tiller where you’d expect it.

The video below shows the build and a test run, plus an analysis of the problems encountered, chief of which is water intrusion. But as [Anton] rightly points out, that’s easily solved by reusing the original driveshaft and mounting the motor above the waterline, like this. Still, we like the look of this, and the idea of knocking around on the water nearly silently seems wonderful.

Thanks for the tip, [Måns]

21 thoughts on “This Electric Outboard Conversion Makes For A Quiet Day On The Water

    1. That’s a lot of extra friction and mechanics that can break. A direct drive like this is often the better choice, but it takes some doing and preventing corrosion is a major challenge. Running the motor in a sealed pod is tricky however at these power levels as you need the cooling

  1. Maybe a bit too challenging preventing corrosion in sea water, but for someone navigating fresh water, this solution may be acceptable. Better management of swarf and maybe better epoxy, and you should be all good?

    1. They are designed for different modes of operation. Trolling motors (gas or electric) are used for fishing so make the boat go slowly and minimize water disturbance. They use a prop with a small pitch which limits the top speed to low single digit mph.

      Outboards (non-trolling) are design operate at the boat’s/hull’s ideal speed, this is usually a much higher speed than fishing speeds, and preventing water disturbance isn’t a high priority. These will have a much more aggressive pitch prop.

      You can get after market props with a more aggressive pitch for trolling motors so they can go faster, although this will have trade offs such as over heating the motor.

  2. Wonder how big his battery was for the total run-time. Having a spare or two might be handy :) to get you back to land, or have a gas generator as a backup to recharge (or setup a curcuit to directly power the motor). I do agree that motor should be out of the water. Lot less headaches for the loss of some efficiency and more noise.

  3. Some of the little lakes and stuff we used to sail on allowed electric trolling motors but no gasoline. I wonder how they would handle this? The few times I’ve interacted with … the kind of person that enforces this stuff… have been challenging. No understanding, no willingness to listen to obvious facts (its electric! I know it looks like a regular outboard but come on!) and forget any humor about such matters.

    1. There’s other reasons besides being gas-powered for banning outboards: wake, wildlife, other users.

      > Nothing beats a day on the lake in a little boat with an outboard motor putt-putting along behind you.

      Uh, a day on the lake in a little SAILboat has that beat by a mile. Just sayin’.

      Nonetheless, an electric outboard is definitely a step forward. Widespread adoption will be dictated by improvements in battery technology, especially their cost.

  4. Take a page from Peter Sripol’s book and put a solar panel covered canopy on the boat. He built a boat that can run as long as there’s sun. At the least with solar panels enough charge can be put in the battery to get a boat like this outboard one back to shore.

    1. I did that on my 2 person kayak. It has an adjustable solar powered canopy. I built the electronics to work only on solar power or only on a backup battery. Motor load control is critical to get the most out of the solar panel, so I manually adjust to get max. power. Actually fun doing that, is like sailing where you always adjust if the wind changes.

  5. Grinding the poles out for hall sensor mounting was probably unnecessary – there is plenty of magnetic field “leaking” into the air to trigger them properly even if just glued on the side of the stator poles themselves, and this grinding introduces an unnecessary air gap, which will lower the efficiency a tiny bit.

  6. “Nothing beats a day on the lake in a little boat with an outboard motor putt-putting along behind you.”
    I’ve worked for a company that built electric boats (usually integrated, with either a more traditional fixed motor and driveshaft or a pod motor) and I can say with certainty the noise of an IC engine doesn’t add anything to the experience and certainly detracts from it once you’ve experienced the alternative. Personally I’m convinced that for leisure boating on smaller waters where you don’t need high-speed or multi-day duration nothing beats electric drive.
    No matter how “quiet” people think their IC engined boat was you always need to raise your voice to have a conversation over the noise (and forget having a conversation over the average outboard). You can whisper to each other on an electric drive boat at full power and be heard (Barring pillocks in IC engined boats nearby).

  7. I can see that he removed the cavitation plate, or did not include one with the motor pod. That plus the long shaft I’m sure are limiting his speed. (I can’t really see the scale very well. Maybe it isn’t as long, but a cavitation or anti-ventilation plate should be roughly level with the keel for best performance.)

  8. Sir don’t paint your epoxy spray it better coating property overall I think project is brilliant although I am a hardcore outboarder and would build. with the power in the old compartment serviceability congratulations and thanks jc

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