Remove the port light completely.
Look carefully to see signs of where the water
is getting in from. Hopefully you can locate a problem. Sometimes port lights leak from water
that actually gets in from elsewhere and travels "downhill" under the lining, sometimes it comes from a leaking frame or leaking screw holes. Or the boat
may be flexing excessively.
Clean all the surfaces to be glued thoroughly. Then wash with acetone on a rag.
We use Sika 291 for a sealant
, but there are others. Don't bother with house caulking.
Put a small blob of sealant
in each screw hold, and a bead of caulking around the entire outside edge of the frame.
Remove any excess.
If this is what you already did, then perhaps a PM to Minaret or MaineSail will give you a better answer.