Yank it out and put in a manual head.

You can buy a "BIC lighter" head on sale at West Marine so cheaply that
it almost doesn't pay to buy the rebuild kit. With light and
intelligent use, you'll get a few years' worth of
flushing for less than the cost to hire a marine electrician to sort
out your current problem.

If you only have one head on a boat, it should be as basic and
trouble-free as possible. The folks who think pumping is unseemly may
not need to go out on your boat. :-)

Elaborate systems should be lmited to vessels with more than one head.