Hi Jim...I see you've just joined our merry little band...welcome aboard.
If you want to keep this toilet, you need to replace the pump
housing (cylinder) and put a rebuild
kit in the pump
. Groco is (as we say in the south) "right proud" of their rebuild kits, so those two items may cost you almost as much or even as much as a "conversion" to the Raritan
PH SuperFlush (current version of their tried and true PHII, which has consistently been the top rated manual toilet since Raritan
introduced it in 1983) Raritan PH SuperFlush
The "conversion" replaces everything BUT the bowl, seat and lid...and the mounting bolt pattern on the base should match those on your HF. Hopkins Carter Marine--formerly owned by longtime forum member
HopCar--seems to be the only retailer who has it and their price
is quite reasonable. Raritan PH Super Flush Conversion Kit #P103
You'll love the PH...it moves twice the bowl contents in half the pumping and will easily provide 25 years of reliable trouble-free service
if you just keep it well lubricated, replace the joker valve annually and put a rebuild kit (about $60) in it every 5-6 years.
Btw...glad you're finding my book useful!