Folks with boats that sit in the ocean docked all the time use Zinc that
is bolted to the hull of the boat
because of electrolysis... I think a piece of zinc in one of the hoses
with a wire attached to the motor
when the hose leads into might be a way to do this.. Maybe if you had
access to a heliarc welder you
could use aluminum wire and tack it just inside the water outlet or
inlet whichever works best for access
of the wire and which hose would support the zinc's presence without
creating a blockage that would cause
overheating..  just my 2 cents... Alan