DIY Electric Outboards
Building a cruising electric outboard that costs less than a new gas outboard (PT 1)
Article by Jerry Culik
Say I’m in the market for a small outboard. What are my options? A reliable Honda 2.3 now lists for over $1,000; a 4-hp Yamaha is around $1,500; and a 6-hp Mercury will cost around $1,900. Great motors, but they need gas and oil changes. The Yammy and Merc also need timely impeller maintenance, and they’re all noisy. Electric outboards eliminate the noise and the hassles. They don’t need gas, don’t need maintenance, and can even be charged up by a small solar panel out on the water. But electric outboards are expensive—a 1.1-kW Torqeedo Travel S lists for $2,998; an ePropulsion Navy 3-kW outboard with a 3 kW-hr battery totals around $5,000. Since I’m a very frugal sailor, I want to build a cruising electric outboard that costs less than a new gas outboard, and a lot less than an off-the-shelf electric. And it’s got to look good on my trailersailer and won’t advertise “expensive electric” to thieves.
Unfortunately, there is very little information about DIY electric outboards. In 2010 Charles Mathys published My Electric Boats, which described all of the gas-to-electric conversions he did over 25 years. He began with a 15-hp Johnson outboard leg, and a “series-wound” DC golf cart motor, and by the end of his journey he opined that a 3-phase brushless motor—the kind Torqeedo and ePropulsion outboards use—was his best and most power-efficient “experiment”… if only he had a reliable controller to power it. And while the information he provides on specific motors may be dated, his book still provides a lot of ideas and plenty of inspiration.
The subject for my “recycling” project is a thirty-year-old 6-hp Johnson. It was a clean, complete motor I acquired at a local auction for $25. It had one obvious problem—it was “locked up.” To folks who restore old cars, trucks, tractors, and outboard motors, this isn’t necessarily fatal because liberal applications of WD-40—and muscle —have freed many a frozen engine. When I got the outboard home I cleaned up the block and drained the oil from the lower gearcase to look for seal problems. I removed the spark plugs and then began applying PB Blaster to try to free up the pistons. My fears that this motor had gone for a swim were confirmed when I found corrosion on the reed valves that are hidden behind the carburetor. Unfortunately, the more I dug into the engine, the worse things looked. Pretty soon I had a box of engine parts and a good “lower leg,” with a working F-N-R transmission and shifter, water pump, and tiller with cable throttle controls. And although working on “vintage” outboards is fun, contemporary 4-cycles and electrics are cleaner and better for the environment. So rather than rebuilding the 2-cycle powerhead, it was time for Plan B—electrification. Should be a pretty straightforward process—just pull out the old engine, add a motor, controller, battery, cables, and assorted fuses and switches…
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