Help installing new skylights-gasket and sealant

[RedRocket]

1991 Maxum 2300 SCR with 2 skylights on fore deck, approx. 14 inches by 24 inches each. I have new ones custom made and ready to intsall. Originally Maxum used about a 3/4 inch rubber gasket all around then sealed with a black rubbery sealant/caulking compound. Instead of making new rubber gaskets, I would like to use Permatex Form A Gasket to set them in and then seal/caulk with 3M 4200 as previously recommended. The Form A Gasket will be much easier to do then buying 2 large rubber pieces then trying to precisely cut them. Note, I have been using Marine Goop for many things around the house and boat. Comments please. Thanks mike

[ShoreAcres]

I don't know much about the gaskets, but I am interested in where you had these made and how much it cost. Mine are cracked of course on my 1990 2700 SCR. I think they are very similar curved plexiglass though.

[RedRocket]

Mine are not like yours. Mine are totally flat. Your curved down portion on mine is simply painted so from a distance, mine would look like yours. Suggest, as I did, take them out and take them to a plastics specialist place. Obviously yours would cost more than mine but I'm sure they can be done. I paid $204 for my two.

Now for the gasket/sealing/caulking situation, I think I have found my answer. I purchased 2 tubes of 3M Marine Grade Silicone Sealant. Its specifically states its OK for being used as a gasket on plexiglas. I also did buy 3M 4200 in white to use as caulking.

[shrew]

I would use 3M 4000UV instead of 4200 or 5200. 4200 is a semi-permanent adhesive/caulk, while 5200 is a more permanent adhesive/caulk. Both are suitable for below waterline use. Neither are UV resistant. The 3M 4000 UV is specifically recommended for deck and rail hardware and will not breakdown in UV, unlike 4200 and 5200 which will break down in UV over time.

4000UV is basically 4200 which is UV resistant.

[RedRocket]

Job is mostly done. I did have trouble using the 3M product and believe the stock from my store was very old. So a local guy recommended I use polyurethane and I used the PL Premium product basically to replace the rubber gasket. The new windows fit perfectly-thanks Canus Plastics here in Ottawa. I still have to fill in the gap between the boat deck and the skylight, replace black caps on screw heads, obviously clean up old glue and maybe touch up here and there with a black paint. It has rained and there is no leakage. The PL Premium is tan in color and my local said that Lepage makes polyurethane in black so I'll use that to fill in the gaps.