This is the old head. The seal on the handle shaft constantly leaked when pumping.
I finally replaced the old and original head with a very nice Raritan PH II head. Flush action is quite positive.
In the process of installation I reversed the assembly such that the flush handle and valve are on the left side (toward the aft) next to the bulkhead and out of the way. If left on the right side I would have had to significantly shorten the flush handle to keep it from being in the way. The installation instructions don't say anything about reversing the assembly but it's a straightforward swap that seems to work fine.
Because the outlet hose is also on the left and within inches of the mahogony bulkhead it requires a very careful measurement and hole through the bulkhead. If I hadn't reversed the assembly I would have had to extend the outlet hose to reach the fitting on the PHII head. Notice that the old hole in the mahogony bulkhead now has a patch over it.
The first flush cost me a little over 0.3BU (one "Boating Unit" = $1000) but the rest of the flushes are free, or "all downhill from there."
This is the whole thing.