If you had my very think Teflon Grease (instead of the thicker stuff that I really have from SuperLube :^).

Seriously -- ONE THING, if you try to pump overboard with the deck fitting open on our system, we don't get suction enough for the lift; AND, probably more germain to your issue, JNorth: If you have that problem again, try to snake down to the tank from the deck OR simply squirt a quick blast with a hose just to free the solid, inpentrable effluent (a/k/a turd) from the orfice. ;^)