Compression trouble

My 1994 Evirude 150 Horsepower engine starts and runs well. I recently did a <br />compression check on the motor and the right side of the engine registered 95 psi on <br />all three cylinders and only 87 on the left side on all 3 cylinders. The only other problem<br />the engine has ever had was some carborator work done last summer. I was <br />wondering if the engine needs a rebuild (new rings, pistons) or if it could be the head<br />gaskets or something else? I also do not know what a routine fair rebuild price should <br />be? Any help would be appreciated.<br />Thanks, <br />Rick

Re: Compression trouble

If it ain't giving any troubles, leave it alone. The lower compression readings could be from a weak battery, corroded connections or a cheap compression gauge. The slower the flywheel spins, the lower compression you will have. There isn't enough difference between the cylinders to warrant a rebuild.

Re: Compression trouble

When was the last time it was decarboned?<br /><br />Except for that possibility I agree with Capt. Ken's comments.

Re: Compression trouble

Rick..... Many of the V/6 OMC engines give a different (slightly lower) reading on the left (port) bank for some reason (This includes your engine). I questioned a factory rep about it one time and received a polite but rather vague reply that it was due to the design of the crankshaft and the port timing.<br /><br />Although the above reply didn't make too much sense to me, the bottom line is that it's normal and not something to be concerned about.<br /><br />The compression on many of the engines (yours included) has been lowered to compensate for the poor quality of fuel we've been receiving for many years now. Compression of past years was up around 125 psi (in that area), but has been lowered to approximately 90 psi, a reading that you're encountering. It appears that you have nothing to be concerned about at the present time.<br /><br />However, keep tabs on the compression just in case, and try another gauge.

Re: Compression trouble

Thanks for the advice. I was thinking that the compression should have been around 110. Motor was last decarbed in September of 2002.

Re: Compression trouble

Rick, <br />I have a 89 225 with compression slighty lower than yours. I was once told by a dealer than when it drops below 90, it's usually time to consider rebuilding. That was 2 years ago and I'm still running it. Considering the cost to rebuild or repower, I will continue to run it. Take Ken's advice, if it's running and doesn't give you any problems, don't worry about it. Run some Yamaha Ring Free through it if you want. It's expensive but supposed to be the best. It may help.