An electric inboard-outboard conversion that flies!

There are are fair number of YouTube videos and other instructionals that cover the idea of converting a fossil fuel outboard to an electric, but not many that detail converting a standard inboard/outboard setup to electric powered.

That’s why we like this one by Scott Masterson of Houston. But before we get to the I/O conversion, a little bit about Scott.

He is the owner of Stealth Electric Outboards, which makes electric motors equivalent to a Yamaha 40. Scott actually orders Yamaha 40 HP motors from an OEM with everything except the powerhead. He puts in an electric motor using mounts and other customizations he has developed over the past couple of years through lots of experimentation.

For all intents and purposes it looks like a gas outboard. The controls are even the same, aside from a few concealed modifications Scott incorporates. Stealth was launched last year and Scott is fielding orders for the Stealth 40 from as far away as Sweden.

Here’s a video giving you a full tour of how it looks when it’s completed and ready for shipping.

Scott didn’t start with the Stealth – that is where he has ended up.

Where he started was with Scott’s wife suggesting that they buy an old pontoon boat. Scott wasn’t even a boater, but they live near a lake and it seemed like a pleasant way to spend time together, out on the water.

Well, as with many used boats, there were numerous unexpected problems and Scott, not surprisingly, got fed up dealing with them.

Scott is an inveterate tinkerer, so he got to the idea of converting the pontoon to electric drive. He went and bought what he describes as ‘a golf cart motor on steroids’ and converted the outboard to electric.

He hasn’t had a problem with the boat since. In fact, he found that cruising around at the leisurely pace of a pontoon boat was even more pleasurable without the sound and fumes of a gas burner. (And worrying what might conk out next.)

Enough pontoon boat. Time to crank up the power!

Speed, however, has its own pleasures, and Scott decided to see what could happen with more power.

So he purchased a brand new 17.5 foot Bayliner, ripped out the brand new Mercruiser 3.0 litre motor and replaced it with a high torque motor from the HPEV company that is designed for use in mining vehicles: the AC-34 X 2, a 100 kW/147 hp permanent magnet 3 phase AC induction oil cooled motor.

Scott set to work re-rigging the Bayliner. You can see in the video below the things that needed to be done to fully switch things over. They are carefully detailed in the video and pointed out as Scott does a tour of the install. Basically, though, he constructed an adaptor for the new motor to fit the existing shaft, threw in some used Tesla batteries that had previously been in Mercedes Smart Car EVs…and had himself an electric I/O.

An electric I/O that goes almost 60 km/h (35 knots/40 mph). You can see it in action in all of its next-to-silent glory in the second video.

This video is of Scott taking the boat out in the spring after the conversion and noting all of the things he doesn’t have to worry about to put it in the water and get going.

  • Check engine oil level.
  • Check power steering fluid level.
  • Check the coolant level.
  • Change Engine Oil and Filter.
  • Check condition of spark plugs, wires, distributor, and rotor.
  • Replace the fuel filter.
  • Clean the flame arrestor, IAC muffler and crankcase ventilation hoses.
  • Inspect the PCV valve.
  • Inspect condition and tension of belts.
  • Replace coolant.

As he says, ‘this is how boating was meant to be”

Scott has a great YouTube channel with all kinds of informative videos, and I encourage you again to visit his Stealth Electric Outboard website for details on the electric Stealth 40.

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Photo Credit: Bayliner, inserts excerpted from Scott Masterson video

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3 thoughts on “An electric inboard-outboard conversion that flies!

  • May 8, 2020 at 11:33 pm

    i want to repower my 42ft (19000 displacement, direct drive) sea ray with electric. I’m being told i can expect no better than like 27 miles range and 2hrs drive time.

    Can you do better?


    • September 12, 2020 at 7:29 pm

      Hi Paul, I have the same question with a smaller sea ray (350 express cruiser). Not too concerned about a flashy top speed, but it will have to be able to handle weather in the Santa Barbara Channel. If you have any fruitful input, please contact me. Good luck to us both.

  • April 22, 2023 at 9:08 pm

    Scott, I have a 24’ Bayliner Discovery. Inboard/outboard has a 5.7 with. Bravo 3.
    Could I replace engine with electric and use the outdrive portion???


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