Main reason is a 20 yr old obsolete toilet that's
worn out. The wet/dry valve has broken, No parts other than a "universal" rebuild kit from Jabsco that fits several obsolete tolets have been available for it for at least 10 years. Which means that it cannot be repaired. It's time for a new toilet.Wet/dry valves can fail, even in new toilets...which is why the seacock MUST always be closed when no one is aboard...seacocks left open are the #1 cause of boats sinking their slips. But you also need to protect against it while you're aboard...so when you replace the toilet, you should install a vented loop in the head intake--not between the thru-hull and the pump, but between the pump and the bowl. The only question remaining is which toilet is the best choice for a replacement. IMO, that's the Raritan PH II...or the PHC (same pump on a compact base to fit in a smaller space)...rated the best manual toilet under $500 for a couple of decades.