4.3L Mercruiser Compression question

Hello Everyone,

So I recently purchased a 88 Sea Ray Bow Rider with a 4.3L V-6. After buying the boat I took it aight to a marine shop and had the engine and outboard checked out. So I had alot of work done on the outdrive replaced everything from ujoints to drive shafts. But my question is the shop tech showed me the results of a compression test and one bank of cylinders is reading 180 and the other is reading 160-162. The tech thought that a hard run on the water may clean out any carbon and help balance the numbers. He also said I should run sea foam in the fuel and crankcase to clean up the motor.

Should I be worried about the difference in numbers from one side of the engine to the other? Would any sealing additives work to help balance it out? The motor starts easily and seems to idle fine, a lil rough on the trailer but i suspect the motor has sat for sometime. I haven't had it out on the water yet. Any opinions or info would be really appreciated.

Re: 4.3L Mercruiser Compression question

Those numbers sound ok... I would say what you have been told is good information. Engines don't like sitting around doing nothing. A good run should have it running sweet. a little seafoam in the tank won't hurt either.

Chris.....

Re: 4.3L Mercruiser Compression question

Although your readings are OK, the fact that one side is consistently higher than the other would warrant further investigation.

A cylinder leak test would be the next step, as that would be more revealing than a compression test.

Re: 4.3L Mercruiser Compression question

I read somewhere that even readings on one-sided a bit off from the other is likely to be machining variances after an overhaul. And the tech did say this engine has been overhauled already. I just think its odd I've never seen numbers so even and consistent like that. Each side is within 10% of each other.

The shop tuned the engine & carb into spec. The engine feels a bit rough at idle but the shop says that engine is infamous for balance issues. I'm going to take it out Sunday and give it a good run.