You can use 5200 or Boatlife. 5200 is for bonding and sealing. I wouldn't use 5200 on plastic parts (such as portholes) that may need replacement someday because the plastic may break before you get the caulk to lift. Boatlife is only for sealing and will not really glue parts together (well, it can be tough to remove but nothing like 5200 is). Either one will do you well for deck hardware.

Boatlife will cure faster if wet and spritzing with water will put a skin on the bead and also jump start the curing. Use this for areas you caulk and then need to paint over...it will reduce the time before you can lay a brush on it without disturbing the caulk. I've done this many times.