I replaced all of my glued in port lights
on my 79 C&C 38 Landfall last year. The ports cost me $110 including shipping from a local plastic dealer PLastic Supply in Tacoma, WA. (800) 832-6774.
I made paterns of the original port lights
, and had a local plastics supply cut new ones. Removed old ports and cleaned all old sealant out of the cut outs. Next I fitted new ports to fit with about 3/16ths clearance around new port light, I did one side of boat one day and turned it around in slip for the other side. Once I had a good fit on the port lights
I taped every place I did not want sealant. Sealant and me don't mix I seem to get it everyplace but where it should be. Next I primed the cut outs and a 3/4 to 1 inch wide stripe on the new lights
along with the edge with Sika Primer 209d. This stuff dries fast and is cleaned up with acetone. Next was to lay a tall bead (1/2inch)down the outer 1/4 of the window cutout with Sikaflex 295UV. Press the new port light into place and smooth squeezed out sealant with a tongue depressor (finger also works) filling in areas that are shy of sealant. You want all voids to be fill (no air pockets). Do this on both sides of the port. The sealant will set in about 30 minutes and be fully cured in about 24-48 hours.
This is the same proceedure used when boats are built new, from what I have been told. So far no leaks.