85' mercruiser 3.0l compression

[Doug12992]

Hello i just bought a 1985 sea sprite with 140 mercruiser with a cylinder compression of 1-125, 2-125, 3-150, 4-125... motor idles well but are these numbers okay or should i be looking to rebuild the motor in the next couple of years?

 

[proshadetree]

Re: 85' mercruiser 3.0l compression

I do not understand why one cylinder is high, normally dont do that. I personally would run it until I had a problem.

 

[Bondo]

Re: 85' mercruiser 3.0l compression

but are these numbers okay

Ayuh,... Not bad, at All...

 

[Don S]

Re: 85' mercruiser 3.0l compression

I do not understand why one cylinder is high, normally dont do that.

It isn't, he has 3 that are low, the 150 is normal.

 

[Doug12992]

Re: 85' mercruiser 3.0l compression

yeah im just using it to fish so i hope the motor will last a few more years. any clue on why one cylinder is higher?

 

[fishrdan]

Re: 85' mercruiser 3.0l compression

any clue on why one cylinder is higher?

Cylinder wear, rings, valve problems on the other cylinders???

If it's running good I wouldn't worry about it, seems fairly consistant except for the one high cylinder. My ol' 73 140 had similar compression readings (something like 125, 120, 140, 125) and it ran fine.

 

[proshadetree]

Re: 85' mercruiser 3.0l compression

It isn't, he has 3 that are low, the 150 is normal.

I was wondering why one stayed high with three low. Most times one goes low valve or ring/piston. Then two low cylinder head or gasket. Three low one higher or normal is just kinda weird.

 

[Doug12992]

Re: 85' mercruiser 3.0l compression

if it comes a problem i'll have my dad look at it. he's a GM mechanic and will have more of a clue then me.

 

[tschmidty]

Re: 85' mercruiser 3.0l compression

It could be lots of things causing one to stay high, but definitely nothing to worry about.