Salt water damaged Oliver "J" model water pump housings can be repaired for re-use again.   These housings are in very short supply!

In the middle of the picture are:

Oliver J water pump impeller; Mercury Mark 20 water pump cover liner; Scott Atwater 7.5 hp water pump housing liner.

With some retrofitting, epoxy, grinding of the impeller blades, and a lot of luck....Ollie will run cool once more.