7.4 mercruiser compression problem

G

goldenboylate4u

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I am in the process of purchasing a 2000- 340 sundancer with twin 7.4 mercruiser engines. mechanic discovered starboard engine with low compression in 1 cylinder. motor was pulled, heads removed and determination was made that valve job was needed. motor had some water in top end. mechanic stated that valve job would correct the problem. could i be in for problems down the road with this? should motor be replaced? engine has 450 hrs on it. thanks
 
Bt Doctur

Bt Doctur

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Aug 29, 2004
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Re: 7.4 mercruiser compression problem

Need a better explanation on how a valve job will cure water intrusion.
Valve job might cure a problem that happened from water intrusion but not the other way around.
 
Don S

Don S

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Re: 7.4 mercruiser compression problem

I agree with BT, the valve job will cure the low compression, which was caused by water, but I would bet money you have a salt water boat there and the exhuast manifold and risers caused the water intrusion.
IF that is the case, you very well could need new manifolds and risers on BOTH engines.
 
G

goldenboylate4u

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Re: 7.4 mercruiser compression problem

according to the mechanic, tulipvalve went bad, risers and manifolds were replaced about 2-3 years ago. he said they still looked good. where did the water come from if risers-manifolds are good?
 
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