1980 Evinrude 4hp

I had a strange situation out on the lake. My 4hp motor was running fine then suddenly started running very rough for a few seconds. Then it made a hard mechanical 'clink' sound with a sudden motor stop. I tried to pull the starter cord but the motor was locked up. I took the cover off and tried to manually turn the fly wheel but it wouldn't move so I grabbed the fly wheel with both hands and 'rocked' it quickly back and forth. It gradually loosened up then finally let go. It felt like a mechanical part released. I turned the flywheel a couple of times then pulled the starter cord and it fired right up. It runs fine but seems to have a little less power than before at high throttle.

Any ideas?

Re: 1980 Evinrude 4hp

Broken piston ring. Small piece escaped and jammed the piston. You eventually released it and it fell down the exhaust. You now have a broken ring, a badly damaged piston, and damage to the bore as well probably. Compression will be very low if you test it.

Well you said any ideas

Re: 1980 Evinrude 4hp

very likely.

Re: 1980 Evinrude 4hp

Vic.S said:

Broken piston ring. Small piece escaped and jammed the piston. You eventually released it and it fell down the exhaust. You now have a broken ring, a badly damaged piston, and damage to the bore as well probably. Compression will be very low if you test it.

Well you said any ideas

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Any ideas about what could have caused it?

Re: 1980 Evinrude 4hp

Thanks for the tip. I've had this motor out on the lake quite a few times since then running it all day. What would be some other symptoms of this problem?