Reply To: Evinrude model U

[Tom]

The U Speeditwin came out for the 1928 model year, and had an above water muffler. The ’29 had a number before the U, and had underwater exhaust. Which does yours have?

The ’28 U series had roller bearings on the main and crank pins, I think that was the first year for Evinrude to do that. Coils are shared with opposed twin Evinrudes of the same era. Some of the Fastwin 12 and 14 hp motors of ’28 and ’29 had aluminum hubbed flywheels, which didn’t hold up well. If yours has a steel hub riveted in, all the better. And like mentioned above, carbs and air horns are getting hard to find.

The cooling system works on a vented propeller. When spinning, the vacuum generated at the outlets of the prop pull cooling water up through the motor, then back down. For this to work, the water tube connections need to be airtight or nearly so. The original tubing and compression nuts were aluminum. Many have been replaced with copper. The compression nuts are NOT the same as those you can purchase today. So if there are copper lines or brass compression nuts on your motor, you’ll need to do some work. There are two V-shaped fittings on the back of the motor. One is supply, one is return. I’ve seen these set up backwards, so water enters the top of the cylinders and returns through the bottom fittings. Be sure yours isn’t set up this way. IIRC, the top V-fitting is the supply, the bottom is the return, but check that with some compressed air.

Be sure the cotter pins which retain the wrist pins are intact. Once unstuck, inspect the pistons carefully to assess their condition. Broken ring lands are not uncommon in my experience.

Good luck with the motor, these sound GREAT when they’re running!

T