bertram31.com

Folks,
Closed / Freshwater cooled Merc 454's w/ center risers

I've change risers several times but can't recall ever knowing a marine mechanics tried true and best practice for gasket installation.

First:
Sealant, Use it or not? RTV? The gaskets I bought are OEM Merc or quicksilver and have a heavy silver coating that I believe is meant to be used without sealant. Didn't notice if there were instructions yet.

Second:
Block off plates, I bought SS block off plates. Then noticed that I had not installed them previously. Maybe the block off OEM gaskets said I didn't need to use them. Are SS block off plates necessary, or is there a special gasket that does the block off job with one piece.

Regards,
Mike Dolan
www.lightningshack.com

i use "perfect seal" even though the instructions say not to. the one time i didnt...they leaked. once i filled the unwanted openings with marine tex...which worked . engines are 25 years old and have never had block off plates....but if i had them id use them

ASSUMING THAT THE LOWER MANIFOLD IS FRESHWATER COOLED. Use the blockoff plates and two standard gaskets. Use Aviation Permatex on the gaskets. DO NOT USE RTV. There is a gasket that supposedly does it all. DO NOT USE IT. It will fail within 5 - 10 hours and trash your engine. This comes from several years of painful experience with those piece of crap manifolds on a friend's boat. He is a good mechanic and tried all of the other fixes. This was the ultimate solution.