Thanks Kevin - that is so helpful. My water tank is to starboard. I, unfortunately did not read about the longer screw situation until after I had this problem, though it seems to have preceded my purchase (based on the water stain running down the wooden bulkhead). I may well have a hole in my water tank and the seeming fix with taping the portlight just was coincident with either lack of heeling sufficiently or tank water level lowering enough to no longer leak. I'll give it a look, but this information makes the leak seem much less mysterious.
Brenda
Brenda