Riser Gasket Gas

[MikeD@Lightningshack]

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

[randall]

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

[Rawleigh]

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.