Roll your own: does it make sense to build your own outboard?
You can build your own outboard for less than $200, but should you?
Assembling your own outboard motor using a 4-stroke engine (often sourced from a lawnmower, pressure washer, or small generator) is a popular DIY project among budget boaters and tinkerers.
I did this myself a few years ago, and I have to admit, it turned out better than I imagined it would. But what is the average person looking at if they want to do their own conversion, and what are the pros and cons?
The overall plan typically involves mounting a vertical shaft engine to a salvaged outboard lower unit (gearbox, propeller, and leg), possibly fabricating brackets, extending the driveshaft, and adding controls. My personal creation consists of a Briggs and Stratton pressure washer engine that I got from Marketplace for $25, married to the midsection and lower of an old Ted Williams 5.5 horsepower 2 stroke from the 1970s. It was cheap and a fun project that saved money, but it was far from plug-and-play.
INSTANT VERDICT, SUBJECT TO CHANGE:
THE GOOD: Style points for being able to say you made your own outboard. Knowing it thoroughly inside and out and being able to fix any potential issues. Cheap.
THE BAD: Well, if you hate repairing machines, you probably won't like building one from secondhand parts.
THE VERDICT: I'm a glutton for punishment, so I'm doing it a second time!
Here are the main pros and cons I've found based on what I did.
Pros
- Significant cost savings — You can often build one for under $100–$400 using scavenged parts (e.g., a free/cheap used lawnmower engine + a junked outboard lower unit), compared to hundreds or thousands for even a small commercial outboard. The Sears/Ted Williams/Eska parts are a dime a dozen, due to the fact that these motors have a solid state ignition in them that inevitably fails, leaving them pretty much useless without a lot of time, effort and money to convert them to CDI aftermarket ignition systems. So, people sell them all the time in non-running condition. The good part is, everything from the powerhead down is tough as nails and will hold up well to just about any motor that will fit on top of them. I've gotten them for as little as $75, and the gearboxes/lower units work flawlessly.
- Ease of repairs and finding parts...or replacing altogether — 4-stroke engines are more familiar to many...and parts are easy to find. For example, I got a carburetor with an idle screw from Amazon for my Briggs and Stratton 190cc vertical shaft engine. That made it idle much smoother than the one that came with the engine, which was unreliable and hard to keep running. Plus, any lawn mower repair shop can work on my outboard, and if I decide it's not worth fixing, I get another motor off of Facebook and swap it out. Easy.
- Reliability and longevity potential — With proper setup, 4-strokes are easier to start in many cases, and they tend to run a long time with minimal care. You do have the added variable of the quality of conversion, but mine has functioned reliably for a few years now with minimal fuss.
- Customization and satisfaction — Full control over the build lets you tailor power...you can build something smaller for lightweight boats, or a heavier setup to fight current and winds. Plus, many DIYers enjoy the engineering challenge and learning experience.
- Eco-friendlier option — Lower emissions make it more suitable for restricted waters compared to old 2-stroke setups.
- You don't have to care about what happens to it — Since you literally made it from junk, you can run it into the ground and smash it to bits. It's practically disposable!
But, it's not all sunshine and rainbows.
Cons
- Complexity and fabrication required — Aligning the engine to the lower unit, dealing with shaft direction/speed mismatches, building sturdy mounts, and creating throttle/steering controls takes serious mechanical skill, tools, and trial-and-error. Many builds fail initially. If you don't have the patience for trial and error, then this probably isn't for you.
- Performance limitations — Homemade versions often lack reverse gear (unless using a geared donor midsection and lower), have slower throttle response, struggle to plane larger boats, and may vibrate excessively or overheat without proper cooling mods. Two stroke boat engines, often water cooled, can run at extreme speeds...my Johnson 9.9 has run at a confirmed 6800 RPM. But, the Briggs and Stratton would be lucky to top out at 4000, and then it would probably be running dangerously fast, risking the valves meeting the pistons for the first time.
- Safety and durability risks — Improper alignment can cause vibrations, shaft failures, or prop loss. The setup may not handle saltwater corrosion well without marine-grade adaptations. Reliability can be hit-or-miss compared to factory outboards, depending on the quality of the conversion.
- Time and frustration — Expect multiple iterations, troubleshooting (e.g., carb tuning, exhaust, mounting stability), and potential breakdowns on the water. Mine was not a quick weekend project. However, this is the age of YouTube, so there are countless videos out there documenting the conversions from which you can glean ideas and understand how to solve common problems.
- Legal and practical issues — May not meet boating regulations in some areas (noise, emissions, certification), harder to insure, and resale value is not going to be ideal. Surprisingly, however, I jokingly offered to sell one and the person I offered it to jumped at the $300 price I jokingly set. That was well above what I had in it. But, truth be told, if you're dealing with broken motors in the first place, then resale value probably isn't your primary concern.
As an Amazon affiliate, I earn from qualifying purchases. All products that I have linked are products that I have purchased directly, or that I am familiar with through other means. I will never link to products of poor or unknown quality.
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