This boat engine of mine has a seawater pump with a rubber impeller.
This sits behind a flat brass face plate with a thin paper gasket.

The impeller is fine but over about 15 to 20 years, the gasket has
disintegrated. The faceplate says on it "Loosen this plate to drain". I
think we spread some Hermetite or similar to take up the slack. It looks
red and old, hard and a tiny bit lumpy.

I have got a new gasket, and will make some spares, but does anyone have
any suggestions better than meths for cleaning off the old sealant. Also
would one normally expect to assemble this dry or use some never setting
smear of goo? It pumps coolish sea water.
--
Bill