Exhaust manifold leak

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PuddleJumper

Petty Officer 1st Class
Joined
Jun 6, 2005
Messages
314
Looking at buying 2001 boat with single 502 mercruiser mpi There is a small leak under the exhaust manifold. I couln't see a crack and there are just droplets there with very slight hint of steam. The mechanic at the marina thinks the problem is a plastic casting plug leaking. States the fix is removal, drill out and put in brass plug. I'm hoping he is right as this would be way cheaper if manifolds (on inspection when they are off) don't need replaced. Has any one heard of this plastic plug issue in mercruiser exh manifolds?
 
Alpheus

Alpheus

Lieutenant Commander
Joined
Aug 3, 2009
Messages
1,757
Re: Exhaust manifold leak

Only plastic I have ever seen is the drain plugs and there is nothing to drill ot unless it broke off inside the manifold. You should ask the seller to have it fixed or at least confirm that the manifold is fine before making a deal.

Its a buyers market right now. Go over that engine with a fine tooth comb...
 
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PuddleJumper

Petty Officer 1st Class
Joined
Jun 6, 2005
Messages
314
Re: Exhaust manifold leak

I already factored new exh manifolds into the purchase price. Also contingent on compression test and drive inspection. Just wondered if anyone had encountered this plastic plug issue.
 
P

PuddleJumper

Petty Officer 1st Class
Joined
Jun 6, 2005
Messages
314
Re: Exhaust manifold leak

Just an informational follow up to complet this post. Turns out the mechanic was correct. There are plastic castin plugs on block side of manifold. The mechanic said they tend to leak if motor overheated once. ( as in toasted impellor) Tapped and placed brass plugs. All fixed.
 
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