With all the shifting, tossing, turning, twisting, and other such contortions that happen on a boat, the predictability of pressure and gravity go in the toilet. The consequence? Most marine heads are easily gummed up. When this happens, and you're at sea, it is really tough to call a plummer over. Heads are the bane of voyagers. Thier construction, to support the unique marine environment, make them prone to nasty smells and backed up lines.
In the really old days, at the front of the boat, there was an open floor and people just did their thing (since it was at the head of the boat, it became known as the head). Over time, people started to want some privicy, and to be out of the elements, which beget the bucket approach. This wasn't too much different than what was happening on land. Then, as the land seating systems improved, people wanted full on seats on boats and places to store "the stuff" until proper disposal was possible. This ushered forth full on house like toilets on a boat. Alas, a boat isn't a house (although in terms of possibilities, a boat is more like a house than a house could ever be like a boat). Hence, head problems.
With self-sufficency being paramount to us, we have decided to remove the marine head we have on the boat and replacing it with a modern-porta-potty. Before you dwell too much on the "Porta Johns" at a rock concert, you need to know that when properly maintained, these self contained units are far superior in terms of maintenance, durability, and smell than almost every marine head.
So, there you have it ... we plan on switching out the standard marine head for a trouble free porta-potty system with the most trivial of mechanics. It will become the daily job of someone on the boat to deftly dispose of "the stuff" in the proper place (at sea, it's the sea).