Oversize rings for low compression worth it?

[Bradley_G]

Have a 78 Johnson 30HP that has low compression. Was working fine last year, then all the sudden went low. one mechanic told me it was not worth the money to rebuild, and to buy a used motor. Another mechanic said it was probably just as easy to go with oversize rings. Anyone have relevant info on the topic?

 

[HighTrim]

Re: Oversize rings for low compression worth it?

Well we need more info. What happened? Did it overheat? Did you pull the head and covers and inspect?

Low on both, or just 1?

If all that is wrong is a blown gaket, might be worth it right.

 

[Bradley_G]

Re: Oversize rings for low compression worth it?

Well we need more info. What happened? Did it overheat? Did you pull the head and covers and inspect?

Low on both, or just 1?

If all that is wrong is a blown gaket, might be worth it right.

not actually sure. didn't sound the alarm or feel hot, no smoking, was running on plane and it just lost the power slowly, brought down to idle, turned it off and it wouldn't stay running anymore. compression low in both cylinders. Have not pulled head but may do that tomorrow. anything in specific I should look for as I'm pulling?

 

[HighTrim]

Re: Oversize rings for low compression worth it?

Start by looking for a damaged head gasket, between cylinders.

If not, look at cylinder walls and pistons for gouging

 

[racerone]

Re: Oversize rings for low compression worth it?

No 30 hp listed for 78 model year.--------First thing to do is determine what is wrong.----O/S rings seems to be an extreme measure !!!!

 

[Faztbullet]

Re: Oversize rings for low compression worth it?

O/S rings wont fit a STD piston......