compression question

[searay30]

My port engine has 1060 hours on it. I did a compression check on the engine and one cylinder is is a running a bit low, down about 8%. The engine shows no other kinds of issues, normal operating temps, normal oil consumption and pressures and no leaks. So here is my issue. Do I do a top of the engine repair, valves, rings ETC or a complete engine replacement. I know for experience when I had to replace my starboard engine with a crack block its was very expensive. The boat is a 1989 30 ' sedan bridge with the engine buried mid cabin under the dinette. What's the best plan of action?

 

[Lazy Daze]

Monitor it, but don't do anything right now. It's very normal to have a difference from one cylinder to another. 8% is well within specs for even a newer engine. Now, if you end up seeing two adjacent cylinders BOTH being low...

 

[Xplicitlnck]

What cylinder is it? If it's one of the two middle ones which in sure it is I would check your manifolds and risers to make sure there not leaking. I was down much more then 8% on one cylinder Ayer sitting for the winter but after a good run I got ask the compression back. Valve seats could be a bit dry or you could have a slight leak from manifolds or risers allowing a bit of water into the bottom of the manifold causing the valve seats to rust a little but when you get the motor running it wipes away the rust and seats properly again

 

[Dieseljeff]

Squirt a little oil in the cylinder in question and check the compression again. If it raises then its more than likely the rings.
I wouldn't worry about 8%.

Jeff

 

[Lazy Daze]

Also, was the compression check done with a cold or warm engine? If cold, check it again with a warm engine.