I have a Traveler toilet that sits right on top of a 90 gallon holding
tank. The toilet dumps directly with gravity and works great. The tank
can be emptied with a standard pump-out fitting or I have an electric
pump that I can use to empty the tank directly overboard which of
course I only do if I am offshore where it is legal. The electric pump
pumps from the top of tank with a dip tube to the bottom. The direct
discharge pump and the pump-out set up use separate piping.

I have tried two different pumps both diaphragm types designed to pump
unmacerated waste. The first pump was a Whale and the second is a
Johnson. The problem is the pumps don't prime if even the slightest
piece of crap has gotten into the flapper valves. The two pumps have
differently designed valves but the principle is the same. I
understand that the tank should be completely pumped out and then
rinsed with water so theoretically the pump is cleaned and ready for
the next time but that only seems to work in theory. I am very tired
of taking the pump apart and cleaning the valves every time I want to
use it.

Would I be better off with a macerator pump?