Part Two: Carefully and neatly sealing submersible marine trailer lighting.
After the lights are installed, mate the wiring using twist-on wire connectors.
(better than a quick-connect dealership job)
Ugh, twist-on's...If you can't solder, something like Amazing
Goop might make a non-corrosive seal on them. The 8200 is
polyurethane--don't know how copper likes that stuff. I'd
stay away from ordinary silicone sealant, it has rep for being
corrosive (at least until it's cured).
I like soldering, with liquid vinyl/heatshrink/liquid vinyl/tape
---letting the liquid vinyl dry, each time--on joints.
I go full-gonzo on boat trailer harnesses...spiral wrap wire
lengths with electrical tape, wiring loom over that, with tape
wrap on wiring loom. Lots of zipties/clips to keep it all
tight against frame and shielded from flung road junk. Takes
a while to install that way, but several of my own and
friend's trailers have all lived for years and years of salt
use.