1984 3 liter mercruiser

[rolmops]

Yesterday I did another compression check on my tired old mercruiser and the results were not good. 90-110-110-150 with some oil in the cylinders it goes up to 130-130-130-150 and I made the decision to replace the engine or rebuild it. This will be a winter project.
Is it possible to use a heavier oil and get get slightly better compression to make it through the fall salmon season?
I'm thinking Lucas high mileage oil.
Please give me your opinions.
Thank you ,cornelis.

 

[cr2k]

Re: 1984 3 liter mercruiser

Sounds more like your valves/guides are worn. Could be a little hard on the engine to use thicker oil in cooler weather.

 

[sti1471]

Re: 1984 3 liter mercruiser

I thought that is the compression is above 100 psi then it was in a decent range to use. anything below 110 or 100 needs repair. so it looks like cyl 4 is the only concern. might be a leaky head gasket?

maybe try a bottle of engine restore in your oil. it claims to restore lost cylinder compression. worth a try for $8