Todd, both 4200 and 5200 are adhesives. 5200 was developed to glue decks down to hulls in production boat-building. On our boats, I see absolutely no need to use 5200 anywhere, and I only use 4200 for items like gluing on mounting boards to install a bunch of electrical products rather than screwing directly into the hull. For a sealant, I have used a variety and have come to really enjoy using Pettit's Anchortech Advanced Hybrid Sealant. It is holding up very well to UV, salt, freezing, is paintable, and can be applied down to 20F, and finally, it's reasonably priced. This is my go-to for sealing deck hardware, windows, and things like your door hardware.