I sealed mine by drilling out the rivets holding the deck plate in place,
using sealant under the little deck plate, and more globbed around the slot.
I did all 4 chainplates this way and it has cut down a lot of the water that
leaks in when it rains. I've been on something of a crusade the last few
years hunting down rainwater leaks (and I get plenty of opportunity to find
them here in Seattle!). Other major rainwater leak reductions occurred when
I move the handrails to atop the hatch slide guides, allowing me to
permanently fill 8 holes in the cabintop (though I think some potters came
this way). Another major leak source was Nav lights. On my potter the
sternlight was mounted atop the transom - water just poured in beneath the
light. I moved it to a flush-mount unit just under the rubrail on the
transom, like some of the newer boats. I had to replace my front bicolor
light because the socket wore out, so I just sealed it real well. I had a
tiny leak somewhere in the cockpit drain assembly, but I am just putting the
finishing touches on converting that to a 1.5" drain and I suspect that leak
will go away when I finally clamp on the hose when the 5200 on the backing
plates dries. 3/4" hose sure bends a lot easier than 1.5", but I found an
automotive radiator hose that perfectly does the bends i need to hook up the
fittings.
I still get some water inside, primarily from condensation (even seems to
occur when I have the tarp on it!) but it is greatly reduced. In the coming
weeks I'll eliminate some other known leaks by drilling out the rivets (gosh
I'm beginning to hate rivets) holding my curtain rods up and gluing the rods
in place with 3m 5200. I've noticed some tiny drips around the rivet holes
so I'll repair the gelcoat around these holes.
I've also found that painting the inside of all the lockers with a bright
white paint (I've been using Minwax exterior polyurethane) really helps find
the leaks.