Yep, the complete disassembly of the toilet!The head over a period of months was having a harder and harder time pumping out.  Finally it stopped flushing, so no other alternative other than taking it completely apart to find out the mystery of the marine head.I've never taken one apart or seen one taken apart, so this was completely new territory.  I removed the intake and discharge hoses (yuck), and rubber-banded a plastic bag over the discharge side since it went directly into the holding tank.  Then unbolted the head from the floor and took it outside into the cockpit for further disassembly.Once completely taken apart, the problem become apparent.  There's a rocker valve that pushes a float ball up to seal the air into the toilet that allowed the pump to go from pulling water into the bowl to sealing it and pumping water out.  The rocker had a set screw that had come loose, which allowed the rocker to slip.  Hence the whole discharge function stopped functioning!OK, $80 worth of parts from Groco later and I was ready to reassemble.  (As a brief aside: the Groco rep I talked to on the the phone was the person who actually built my toilet back in 1998!  Talk about customer service).Everything went back together quite easily with the exception of a leaky gasket.  In plumbing there's always a leaky gasket!  In this case, it was the gasket that linked the toilet bowl to the base. I had tightened it too much as is often the case in plumbing problems.  Once you over-tighten a gasket, it collapses and you're out of luck.  I took the bowl off-worried that I had broken the porcelain by overtightening, but hadn't-removed the gasket, cleaned it and put it back on.  Then reassembled the bowl "loosely" this time.  Re-attached the intake and discharge and pumped.  Leaking.  Tighten the bowl a little.  Still leaking.  Tighten a little more.  Leaking, but a little less. Tighten a liiiittttlee more.  Leak stopped.  It's a fine line.Toilet works better than ever and leak has stopped.   All in all, not as bad as I thought it would be and another adventure complete!