3.0 Mercruiser problems

[cpawlowski12]

Just did a compression check. #1 and #4 have 100 psi. Two comes up at 30 and 3 is at ZERO. Bad motor or just a head gasket? Boat has not run since 2006. Oil is OK not milky.
Motor is a 1985, not that that matters much, 3 liter 4 cylinder.
HELP!

 

[Don S]

Re: 3.0 Mercruiser problems

A leakdown test will tell you for sure, but usually a blown head gasket will still have 30-50 psi. To have 0 takes a lot bigger hole. Might as well pull the head and look.

 

[Simoniz]

Re: 3.0 Mercruiser problems

Most likely cause for zero compression in a motor thats not been run for 5 years would be stuck valves.

You might be able to free them up by tapping them with a hammer with the rocker box removed but, even if you free them up, I doubt the engine is in very good shape.

As Don says, whatever happpens, you'll probably have to remove the head so you might as well do it now to see what you're dealing with.

 

[Bondo]

Re: 3.0 Mercruiser problems

Ayuh,... Pop the head off it, 'n you'll have a better idea of just how bad it is....
Sounds like it may, or may Not make it as a rebuildable Core motor...