Replacing ports on my 84' redline yesterday and saw its only a single layer of glass around ports, is this normal? Having port installed strengthens considerably but still seems pretty weak...
It's not actually a single layer of glass, but it is a solid laminate (i.e., no foam core). The glass thickness is only about 1/16" thick, so it is quite flexible. If your boat has the original pop-in deck ports (these were standard on H18s in the mid-1980's) they will flex the deck and cause stress cracks. Even with screw-in ports, the decks will eventually start to crack around the ports because the glass is quite thin.
On my 1985 H18 (also a red line), I reinforced the area around the ports by disassembling the hulls and flipping them upside down on cinder blocks. Then I built up the inside of the hulls around the ports using two or three plys of 1-1/2 oz fiberglass mat and epoxy. Not the easiest job since you're working upside down through the access port, but doing this about doubled the overall thickness of the laminate and made the decks considerably stiffer around the ports, so worth it IMO.
Thanks, my old 80' 18 had a lot of cracking around the ports, this explains why.... This one has virtually none, I'll add stiffing deck to the winter project list