1989 omc cobra 5.7 water in engine and cylinders

[markklaben]

Found my exhuast bellows cracked and just wondering hoping if this could be the problem. My boat sits low in the back. (1988 Fourwinns Sundowner). And when I put the boat into the water I left the tiedown straps on the trailer. Pulled the boat out took the straps off it started fine. Engine got hot never over 210 on the guage. (later found the impeller melted)? Stopped motor/boat rapidly cause it was getting hot and would not start. After cranking engine around six times with only small movement took out the sparkplugs and found all cylinders wet with water. Two of the cylinders spat out water when I cranked it. Drained the oil and found water... Not milky. One cup came out of engine before oil came pumping out. Compression is all the same except one cylinder is about 20 psi lower than the rest. I have a cheap push in compression tester they all ranged around 150 psi except for the one which was just over 120. Any ideas. What do ya all think with the compression the way it is!! <br /><br />Also!!! <br />I took off a exhaust manifold and riser. No sign of leakage here!! There is alot of rust. Is there a way to clean out the rust or is it just wise to replace. I heard about boiling them with "on&off" or mauratic acid. The Manifolds alone are $294.00 each. This manifold was only in production for one year. 1989. And I can not find any after market ones from sierra or GLM catalogs.

 

[WillyBWright]

Re: 1989 omc cobra 5.7 water in engine and cylinders

If the motor got hot, the flappers probably melted. If one got caught sideways in there and restricted the exhaust flow it would run hot plus lack performance.<br /><br />Without those there, your motor might have got a bit of backwash in it. Especially if it's assheavy.<br /><br />Or it got hot enough to warp or crack the heads.<br /><br />If the boat is or was run in saltwater, replace the manifolds. That old and they'd need it one way or another.