exhaust manifold question OMC 800 Stringer v6

rd1002

Cadet
Joined
Mar 21, 2010
Messages
15
Our starboard side exhaust manifold had a crack in it. We had it welded and then where the gasket goes wasn't a perfect flush fit do to the weld. It may not work but we have not been able to find one for the v6 so we thought we would give it a try My question is what type of permatex gasket maker do we use with the regular gasket. We have been told to use the regular gasket then put a form a gasket or permatex on either side of the gasket so it can form a seal. Can't figure out which permatex to use their are many types. Their is even a copper one we were told to use but then someone else said they wouldn't. They were not all boat people but being you all are we would love to have some advice on this please. Also it looked as if one of the four holes or channels on the manifold was blocked almost looked welded closed. It wasn't rust or anything but is that normal or should all four be open it is where it meets with the riser elbow. Is it going to damage our engine if the weld dosen't hold. of course if we noticed the exhaust leak again we would stop immediately. Thanks in advance for the help.
 

carrier82

Petty Officer 2nd Class
Joined
Oct 1, 2013
Messages
118
I used high temperature silicone RTV gasket sealant on my manifold to riser gasket a couple of years ago when I didn't have replacement gaskets available and had to get the job done. I've removed the spark plugs every now and then and checked the cylinders for water but hasn't leaked at all. If it's the manifold to head gasket, that might be more difficult. Don't know about the holes, perhaps a picture would help.
 
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Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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47,309
i wouldnt trust a welded manifold. that is a hydro-locked motor waiting to happen. not to mention if you have just a slow leak, you will eventually damage that cylinder due to rust.
 

Howard Sterndrive

Rear Admiral
Joined
Nov 5, 2008
Messages
4,603
There's an OSCO conversion kit out there. but expensive.

I have never used any kind of sealant on exhaust manifolds. I just buy the thick one piece exhaust gasket. like these:
 
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Redrig

Master Chief Petty Officer
Joined
Oct 13, 2009
Messages
849
i wouldnt trust a welded manifold. that is a hydro-locked motor waiting to happen. not to mention if you have just a slow leak, you will eventually damage that cylinder due to rust.

This. You are gambling with the engine for sure.

At a minimum I would pull off the manfold and riser , and fill them with Acetone to ensure that there is no internal leak.

The Acetone will find its way through any hairline crack much easier than water.
 

Bondo

Moderator
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Apr 17, 2002
Messages
70,469
and then where the gasket goes wasn't a perfect flush fit do to the weld.

Ayuh,.... How much deviation,..??..??

Was it dressed off with a flap wheel,..??

Post a picture with a straight edge, 'n a light behind it,.....

Is the weld high, or the iron low,..??
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
We had it welded and then where the gasket goes wasn't a perfect flush fit do to the weld.
I would get thenmanifold surfaces machined flat and then do a pressure test of the manifold before I would ever trust it.
 
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