I just replaced my access ports with Hobie's newer style 8" round twist-n-seal hatches (part # 7170211). I like this new design with the hinged lid and locking handle that recess flush with the deck.
I have replaced the original rope handled access ports with the screw in style and had a difficult time unscrewing them sometimes especially once sand found it's way into the threads.I first tried the white screw in style and they turned a pale yellow over time and looked bad. Then I replaced them again but this time I installed black ones and they weathered much better.
My new ones are really nice but let me warn you that you will have to cut out some of the fiberglass decking to install as these require a larger cut out size.And you will need to "cope out" some of the flange to fit into that "pocket" on your deck.Take your time to get the right fit.Tape off the deck so not to scratch it with the jig saw base.Cut out 3/8" all around your existing cut out size, than use a drum sander on a cordless drill to smooth your cut and improve your fit.Next,use a grinder with a sanding setup to trim under side of hatch flange to match your deck pocket.The spongy gasket that came with new hatch will try to slide out on the silicon as you tighten your screws so use a paint scrapper to hold it in place and reseal if necessary.You may choose to not use that gasket and just use silicon.
Again,take your time and you will like the results.