All it needs is lubrication
There are two ways to keep a toilet lubricated:You can spend 10 minutes once a year replacing the same lubricant that's in all toilets when they leave the factory, and which lasts at least a full season.Buy a tube of Teflon grease--available from most auto parts stores and swimming pool supply outlets....in fact, I think even Radio Shack carries it. Lift up the top of the pump (all you have to do is loosen the hex nut and lift up the top)...put a healthy squirt of the grease in the pump...pump a couple of times to spread it all over the inside of the pump cylinder...repeat...put the top back on and tighten the hex nut. Should tank you all of 10 minutes, and will keep the pump working smoothly for a full season without the need for any more lubrication. Do it annually--or as much as you use your boat, maybe semi-annually--as preventive maintenance.Or...You can pour a tablespoon of olive oil, mineral oil (baby oil is mineral oil, btw), vegetable oil, or liquid "head lube" down the toilet every couple of weeks for the rest of your life--'cuz anything thin enough to be poured down the bowl is so thin that it washes out again in just a few flushes.Either way, keep the toilet well lubricated and you should get about 5 years relatively trouble-free use out of that toilet. Otoh, if you're planning to do some serious cruising, I can't argue with Steve's suggestion to replace it with a Raritan PH II (which also requires lubrication--all manual toilets do), which is much higher quality toilet. The mounting bolt patterns will not match, but the plumbing should with no problem.