Compression Check left me SAD!!!

[jayard78]

I have been working on a project motor 1980 merc 40hp and have fixed and replaced and fixed many things. A month ago or so I did a compression test and the upper cylinder was 160 psi and the lower was 160 psi. Then after running it about 30 miles or so in a month I had various issues with it running better in the first 20 minutes of run time and not so good after that. I have since done another compression test and I am reading 60 psi on the upper and 150 psi on the lower which makes me very upset. I noticed the gasket on the side of the block is corroded and looks like the seal is not great towards the top of the motor. Could this cause my compression to be bad or did I ffff up my pistons and rings and such?

Should I replace this gasket before I start to.....cry!!!!

I also heard that engine cleaner may free up the pistons a bit or am I dreaming?

I dunno how this happened if it is the pistons/rings and such, I have the impeller replaced and the pee hole has been peeing well. I used 40:1 mixture once in a few gallons and a 50:1 after that. Least I thought so. Please advise me and tell me what I should do.

 

[Laddies]

Re: Compression Check left me SAD!!!

Pull the intake port cover and use a flashlight to check the pistons and rings

 

[jayard78]

Re: Compression Check left me SAD!!!

Right, and where exactly is this port cover and how do I get to it? What am I looking for when I can see in to the pistons?

Do you think running some sea foam throught the engine may bring the compression back up?

Someone had suggested that the carb may have been running too Lean, what you think?

 

[Laddies]

Re: Compression Check left me SAD!!!

Item # 39 http://www.mercruiserparts.com/Show...110&bdesc=CYLINDER+BLOCK+CRANKCASE+AND+COVERS
Seafoam may help if the rings are stuck and yes if the carb is dirty it could have damaged the rings

 

[jayard78]

Re: Compression Check left me SAD!!!

So how do I get a look at these pistons with a flashlight if you dont mind me asking? I am just wondering if this is something quick I can get a peak at or if I need to remove the powerhead. The way the cover is makes it impossible to get a lot of the stuff off the powerhead unless it is removed all together. Like the exhaust manifold for intstance is impossible to get all the bolts out unless the whole powerhead is removed.