Re: auto gaskets usable?
Automotive gaskets (and we are talking mostly head gaskets here) are made from mild steel. The only adverse conditions they face is outer edge between the head and block and that is usually covered with oil residue so not much chance for rust or corrosion.
If you have a closed cooling system in your boat it would be about the same.
But with a raw water cooling system the internal passages are also subject to what ever is in the water with out the protection of antifreeze/coolant.
These will have a shortened life span.
This is why marine gaskets are made from stainless steel where necessary.
