Not the seals
I had a 321 with this problem. Its a common problem with Lewmar portlights and is NOT the seals.Look at the portlight from the outside. See the grey "connector" between the upper and lower frames? This connector seals that joint, and over time it starts deteriorate and leak. Leak where you ask? The frames are hollow extrusions, and the water gets into the hollow center of the lower frame. Now look on the inside of your portlight (with trim ring removed), you will see that there are numerous holes on the inner frame where the inner frame and twist locks mount. The water which pools in the hollow extrusion seeps through these holes, even if they have screws in them (not all the holes in my boat had something screwed into them). I tried siliconing the threads, siliconing the unused holes, etc. It worked for awhile, but in the winter water would get in the hollow, freeze, and push the silicon out. I was never able to fix 100% of the leaks, and had to re-do some number of the fixes every year.IMO, the only way to permanently fix the problem is to remove the entire portlight, disassemble the frame, fill the hollow just below where the connector fits with silicon, and install new connectors.Fair winds,Tim