...

You want a Polysulfide-based sealant. It bonds best to various surface energy levels, and remains flexible when cured. We used BoatLife, but 3M 100 would work too. Look in BoatUS or WestMarine catalog under Polysulfide and go from there.<<

I used Boatlife polysulfide on Stargazer's windows and they've held up for nearly 3 years now. Harvey/Ga M-17 Stargazer #294