I've fought this exact issue on several occasions. One time the oil plug remote drain fitting hit the hull and cracked the pan. Another time the fitting itself was leaking -- I ended up welding the pan, then welding a nut on the inside of the side so I could move the remote oil drain to the side. The pan just sits too close to the bottom of the boat.
Once I resolved those issues, it was still leaking.... from somewhere. I replaced the timing cover gaskets and pulled the engine to inspect the rear seal. Seal seemed good. Replaced valve covers (which were cheapie stamped Summit brand) with some heavy duty cast aluminum ones and new Fel-Pro gaskets. I believe that I elimaniated about 90% of the leaks.... but it still leaks from somewhere. I've just learned to deal with it. I put a cup full of laundry detergent in there when I pull it out every time. Seems to help keep it reasonably clean.
This year I started noticing transmission fluid in the bilge. I've replaced the coolant lines and checked every where else that it could be leaking from. Another mystery. Has leaked about a quart and a half this entire summer (about 120hours.)
Former owner of a 1987 Supra Saltare. Current owner of a Malibu 23LSV.