Well, I suppose if the OP is a machinist like delmarrey or has a friend that can make a part like delmarrey made it would be a fairly cheap
fix. However to have a machinist come to the boat, do all the measuring needed and make the parts
, fit and test plus the new water
pump, not so cheap anymore I think.
What shape is the rest of the engine
Is the heat exchanger
still in good shape?
How about the exhaust cooling
Maybe the OP should check the timing belt to see what shape its in.
These are all things that should be considered of course.