Blown Head Gasket

[Todd Humphreys]

I have a 1982 Johnson 75 hp, and the last time I was out the motor had a really bad miss at idle. A couple of days later I checked the plugs and the top two was rusted. I pulled the water jacket and head see what the inside was like. No. 1 & 2 piston had salt baked on top of them and the third had alot of play in the cylinder. Head gasket was to blame for the water leak. After striping the motor and pulling the pistons, I encountered that pistons no. 2 & 3 were scored and cylinder 3 had a bad scratch the entire length of piston travel. Upon closer inspection of the pistons and rings, on pistons 2 & 3 the pins that keep the rings from rotating were broken off, one was stuck in the ring grove and the other missing. I think that was the culprit of the bad scratch in cylinder 3. Is this common for the pins to break off and cause this kind of damage, or did something else such as carbon or lack of lubrication cause this to happen???

 

[WillyBWright]

Re: Blown Head Gasket

The pins fail on their own on rare occasion. Most of the time it's carbon in the ring groove preventing ring movement and slowly wedging the ring out.

 

[alcan]

Re: Blown Head Gasket

Just stright water intrusion can cause this also.

 

[Todd Humphreys]

Re: Blown Head Gasket

Would you recommend Weisco pistons compared with OMC pistons for durability and longivity?? I'm planing on rebuilding it and its only about $30 more for Weisco. Also is it better to order the pistons and bring them with the block to the machine shop so they can properly bore the cylinder to each piston thus having closer tolerances??