Originally Posted by Gallivanters
She started right up after the usual starter removal & socket wrench routine. I'm pretty sure a bearing is at the heart of the problem because there was a high-pitched squeeking sound for about the first ten seconds when it ran.
Not savoring the idea of breaking the engine apart.
When removing plugs can you turn engine with starter cord? OR/and By putting in gear and turning prop?
Before stripping, suggest drain lube oil, then replace with kerosine(paraffin)turn engine by hand. Drain, add SAE 10 - run engine for couple of minutes. Drain SAE 10 and replace with 10 <> 40 multigrade -- run the engine normally.
Kirk, the Yamaha 15 has a problem with latter day gasoline, eventually causing piston rings to jam open tight - they have a fuel additive called "Ring Free Fuel Additive"
If that does not cure, then if she partially seizes again, you will have to strip completely - the symptoms are also pointing to poor lubrication (blocked oil gallery ??)