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What manifold? Intake or exhaust?
I think that you'll be safe to use what Barr provided.
Okay thanks. It's in brackish water so I'm going with the fiber one.For exhaust manifold either type will work. The metallic one is susceptible to corrosion but if your not in salt water it will be fine.
I read some literature that warns against using sealer on these gaskets.
Jeff
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not sure where this information comes from, but in the "automotive" world, specifically 454 engines in heavy duty applications, they recommend that the exhaust manifolds be surfaced and silicone used in place of gaskets, as this allows for a better heat transfer which gives longer manifold life without cracking, warping or leaking..... in a marine application, the engine isnt getting as hot and isnt getting road spray on it, but i cant see the downside to using silicone in place of a gasket or with a gasket... on marine engines with closed loop cooling I use regular automotive exhaust gaskets without any failures, but i also always surface the manifolds, as its very surprising how warped even new exhaust manifolds can be..<br><br> the use of silicone on the exhaust manifold gasket probably has very little effect either way...<br>
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in all automotive engines we deal with that has cast exhaust manifolds, we dont use gaskets at all, but only silicone as it lowers the chance of an exhaust leak
1. This is strictly a Marine Application.
2. Auto experience such as yours does not matter here.
3. Your automotive application uses TWO (2) bolts/studs per exhaust hole...............Mercruiser does NOT.
4. USE A GASKET. What type is your choice!
The suggestions came from Barr and OSCO, as I recall. Their idea, apparently, is to keep excessive silicone plugging up the outlet holes in the elbow (where water finally meets the exhaust). I've seen one side manifold overheating when the holes on that side plugged up.
That said, water leaking into the motor through the exhaust ports is a far more threatening possibility. I seal the gaskets with a smear of silicone on each side and wait a while for it to set before firing the motor up.
Jeff