The motor in my boat only has enough room under the pan to slip my fingers between the bottom of the hull and the pan, it's a 10 quart Dooley jet boat pan and it uses a GM pan for the rear sump, the pan in the raceboat almost touched the pump intake bolt area (intake was welded in) it all depends on what hull, what the pump is in the boat and how the engine is set in the boat (close driveline, extended DL, double or single joint blah blah blah)
IMO a stocker should clear and I want to say they are normally about 8 1/4" deep from the rail...
GT