1999-mercruiser 5.0L 8-cylinder overheat and 2 cylinder have low/no pressure

jvaulter

Recruit
Joined
Jul 25, 2022
Messages
5
May have screwed up. Took the boat out while it was a bit choppy and the water pump belt decided to jump off overheating the engine. Fast forward I test for spark and fuel good to go there. I test all the cylinders and all good except I am getting no compression (0) on 3 and barely any (~30) the opposite side 4. Thinking I blew a ring or something in those two. So wondering how much work is ahead of me before I start googling repairs or is it worth it just to take it in? Any insight or help is greatly appreciated!
 

Rick Stephens

Admiral
Joined
Aug 13, 2013
Messages
6,118
Valves or piston - I'd bet valves. A rebuild may very well require going through everything if it got hot enough. Block checked for deck flatness. Heads gone over fine tooth comb. Cylinders inspected. Hot enough to get a couple cylinders down to nothing is pretty hot.
 
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