I had the problem on my 1990 25, I removed each window and cleaned them up, got rid of the old bedding compund on the window and the opening. used a solvent to clean the mating surfaces ( I used alcohol) and then used a good marine silicone caulk (don't use the ones that smell of acetic acid) and replaced the ports allowing a little time for the caulk to set up so when you tighten down on the ports screws the silicone does not squeeze out, it forms a gasket.
don't miss the screw holes and screws, a dab of silicone is a good thing.
they have not leaked since this was done, about 8 years now.
