Originally Posted by HeadMistress
True...but you have to keep a tapered fitting jammed tight into the fitting to keep a seal...whereas a "universal" threaded fitting will seal and will cam lock onto any pumpout hose.
I don't think anyone disagrees that the threaded adapters are preferred. The problem is that the commercially available adapters don't fit a significant number of boats that utilize different thread patterns.
The question that was originally posed was from one of the unfortunate with "different" threads on his deck fittings. For those of us in that camp, we have two choices; 1) fabricate a custom adapter that matches the deck threads, or 2) use one of the cone adapters and hold it in place while pumping out.