engine pressure

[toothycritter]

I am looking at a 1997 Carolina Classic with a 454 in it. The boat has been recently surveyed. IT has 640 hours on the motor. What should i expect for compression in each clynder. Should they be all pretty close, should they all be above a certain compression. These are the compression on each (1) - 145, (2) - 140, (3) - 145, (4) - 135, (5) - 140, (6) - 130, (7) - 140, (8) - 130. Any info will help. Thanks in advance

[Laketrotter]

From the compression reading you list, the range fom 130 to 145 you have over 10% difference. This tells me that the motor is ok but not great. You have a couple of cylinders (130psi) that the valves are leaking or worn piston rings. My guess is bad valves from what I experience with GM big block motors. A good engine the compression shouldn't vary by 5%. As for a maximum psi that all depends on the compression ratio of the motor, the higher the ratio the higher your maximum psi would be. The Carolina Classic is a nice boat, I have seem a couple of them around Port Clinton, Ohio.

[Laketrotter]

If its the boat listed at IBoats. It could be a salt water boat, just from his ad saying he flushed the engine with fresh water after using the boat. I would make sure you have a current survey on the hull , motor and outdrive.

[SalmonBum]

I agree about a few of them being on the LOW side. You should take two readings: Start the motor and run fo a few seconds, then another at operation temp.

Also, if you checked the compression and the boat is still winterized, the fogging oil may be giving you a higher reading that it actually is. The fogging oil will help build pressure, so you need to make sur it is ran out to get a good reading.