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KennyNova 08-11-2007 08:20 PM

Corvette engine in boat
I just got my new boat from the states, it's a mastercraft maristar 230vrs.
It has a 96 Corvette 350 engine on board, when I first started it (on water) it overheated pretty fast, then I changed the impeller witch was burned. Started the engine after this operation, it ran great and the temperature was fine!
I took it for a trip and suddenly it started rumbling like it didn't run on all cylinders and the temp went up to 240.F
A friend of mine towed me back, and i opened the oil cap on the valve cover and found water in the oil, after this I disconnected the coil and took compression test, and after testing cylinder #1 the engine started making a knocking sound witch sounded pretty bad.
It's not easy for a norwegian youngster to describe the sound. But does anyone have a clue?? Please!

Kenneth Nęss

302 Z28 08-11-2007 08:39 PM

Sounds as if you may have blown a head gasket. Remove all the plugs and run a compression test on all cylinders. If you did blow a head gasket and you did not remove all the plugs when you ran a compression check it is possible a cylinder had water or coolant in it. When you cranked it over it tried to hydraulic lock and may have bent a rod.


KennyNova 08-11-2007 08:47 PM

I did remove all plugs before I did the test, and no water/coolant came out of any cylinders. are there any ways this could have happen?


302 Z28 08-11-2007 08:54 PM

What readings did you get when you ran the compression test?

KennyNova 08-11-2007 08:57 PM

didn't finish the test because of the sound! but I will come back whit numbers tomorrow, I'm just afraid of destroying the engine even more..

302 Z28 08-11-2007 09:02 PM

Inspect all the plugs, look for one or two that are of a different color or the gaps are closed.


KennyNova 08-12-2007 07:05 AM

Finished the test today, the mid cylinders. (3,4,5,6) had 4-6 bar pressure.
Had a local Chevy guy with me today, he told me that piston rings were destroyed caused of the high temp, and it sounded like a crank bearing or two had serious injury. Ouch! started lifting the engine out today, just have to get a answer from the company in the states that sold me the boat what we can do.

Kenneth Nęss

topfuel 08-14-2007 06:11 PM

Kenny, if it really is a 350 out of a 96 corvette, it is an LT1 or possibly an LT4. The LT1 uses a reversed cooling system. Unless the cooling system of the boat was designed for this engine or modified for it, you will suffer cooling system problems. The quickest way to verify if it is an LT1 or LT4 is to look at the side of the engine block. If you see a "327" casting on the side of the block, it is an LT1. I would definitely recommend not using this type of engine in a marine application. You are asking for problems if you do. I would seek out a standard small block to replace it.


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