1979 Mercruiser exhaust manifolds.

I am rebuilding the heads on my engine. I separated the manifold from the riser and now need to replace the gasket. I noticed that there is a metal gasket the has all holes blocked but has one small bb size opening and a regular gasket with all 3 holes open. Is this normal? I am replacing heads that were cracked due to overheating and broken head gasket. Just making sure this isnt causing any problems before I seal it back up.

and this is all connected to what??????????????????

Get your model and serial number and look up the required parts using the engine parts link at the top of the page...most all have parts have pictures showing details...there are a few blockoff plates from that vintage that I remember having small oddly located holes.

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Gemini_Sosa said:

I separated the manifold from the riser and now need to replace the gasket. I noticed that there is a metal gasket the has all holes blocked but has one small bb size opening and a regular gasket with all 3 holes open. Is this normal?
Need more info.
The small bb sized opening in the elbow gaskets suggests Raw Water cooled, or at minimum, a "half "closed cooling system.

If the elbows are being fed sea water independantly of the manifolds, then the OEM gaskets are required.
Conversely, if the elbows are being fed sea water via the manifold "transfer ports", then the gaskets will need to be fully open for each transfer port.

I am replacing heads that were cracked due to overheating and broken head gasket.
Learn which pistons were used in this 1979 engine, and be sure that you replace the cylinder heads with like combustion chamber volume.
Back in 1979, these may very well be F/T pistons with the 76cc chambers.
Many of the later chambers are only 64cc, and were commonly used the full dished pistons.

The wrong combination (either way) will give you troubles.

Click to expand...

More information and a few photos would be very helpful.





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