Recently I bought a 1984 Hunter 27. When attempting to have the holding tank pumped out, I was told that the fitting (and its cap) was non-standard, preventing pumpout. The cap is a twist lock, half turn type. (Same as the fuel cap). Adapters at the pumpout stations (that I have seen) are of the multi-turn screw type. What is the solution here? Do I need to replace the thru-deck fitting or is there some adapter available for this type? Anybody been there? Thanx!