I recently purchase a 1999 Johnson 2 stoke 15hp engine. Engine looked good inside and under the cover - nice and clean.
Over the weekend I took it out to a place with a 5mph speed restriction where my dad keeps his speed/power boat. The idea being to cruise up and down @ 5mph for a while to test the engine.
After 15mins, the engine just stopped. I kept a close eye on the engine to make sure it was pumping water and it was. I was actually looking at it when it locked up.
- Engine started fine on second pull
- Water was pumping out the back nice and strong
- Fuel appeared to be flowing fine, certainly no blockages in the pipes
- Petrol was mixed perfectly - (I do this all the time on a 75hp 2 stoke)
- I didn't give it any beans. 5 - 6mph according to GPS (Boat was not planing)
- It's not a gear box problem
So I take the pull cord off and remove spark plugs. I ensure the engine is in neutral. I am unable to turn the flywheel, it is totally locked.
I look down the spark plug whole and I can see what looks like a piston ring sticking out from the side of the piston.
What could cause an engine to lockup doing 5 - 6mph?