Compression question
 

Looking at a 290 enticer 454 MPi's. 250 hours. Starboard engine ranges from 135 to 145. Port ranges from 110 to 130. If you take out the one cylinder at 110 it ranges from 125 to 130. 110 seems low, what about a leak down test? What should i be looking for?

all seem low 100 would be like 6 to 1 mechanical

If the lower compression cylinders are the middle ones you should be checking for leaking risers and or gaskets, any signs of rust on the plugs. Leak down will tell you if it needs heads redone or the whole motor. Low hours doesn't mean anything if its had water leaking in exhaust. Good luck and be careful.
Jim

Has the boat been sitting a while?
you want to be within 10% on the compresion test.
you can also check it with a vacoum gage while the engine is running,make sure the vacoum gage needle is not bounching around.

It's actually the #2 cylinder thats at 110. I believe the compression test was done in the spring. It's only been run twice this summer.

It would be a good idea to run the boat and recheck compression

Come to find out when the boat was taken in on trade it was still winterized and the compression check was done before the motor was fired. Before the boat was run starboard ranged from 135-145, port 110-130. After the boat was run (not hot) compression was starboard 150-160, port 145-150. What do you think of that?

good to go

I agree that sounds good.

It just shows the differences you can get between dry cylinders vs. recently run wet cylinders.

I have seen people find low compression cylinders then give the plug hole a little shot of oil to see if the pressure comes up. If it does not raise I think that means the low pressure is due to valves as opposed to rings. I know the rings require a thin film of oil to seal better.

My .02

you are 100% correct!