@njmr2fan, two months, two dips into salt water and over 4,000 miles later they are holding up perfectly. We do trailer every time that we boat. We live on a lake and will have a dock someday but for now we launch and retrieve the boat for every outing. If the LEDs come unglued or stop illuminating I will order two more strips for $14 and it will take perhaps 15 minutes to swap them out.
The total cost was $27 and about 30 minutes. The supplies consisted of two of these
LED Strips, 12 x 18" outdoor wire ties, less than 10' of 16 gauge dual conductor wire and solder and shrink tube that I already had on hand.
I popped out the front trailer side light out on both sides. On my trailer they are installed in rubber grommets. Then I cut the factory wiring and soldered and shrink tubed my oversized 16 gauge wires into the factory wiring splicing the factory wiring back together at this point. Marine grade splice connectors could be used as an alternative. You can substitute any 20 gauge or heavier two conductor wire that you may have laying around. This end is hidden so if you are not comfortable soldering they would work just as well.
The LED strips have a short wire leader. I soldered and shrink tubed my 16 gauge wire to this leader. I used a third larger and longer piece of shrink tubing to cover the area where the two wires were split on one side. If it I were doing it again I would use this outer shrink tubing on both sides. Snap style connectors are available to make the connection to the LED strips. some have leads already attached. I prefer the solid and more water tight connection provided by soldering and shrink tubing.
If you do not have tools for soldering and shrink tubing then this would be a decent start for $30 that will allow you to do a wide variety of electrical projects on your boat and make you a hero when you repair jewelry;
30 / 130 watt soldering gun - use 30 watts for this project and other small projects, 130 watts would be reserved for larger wires.
.35 ounces of silver solder - silver is stronger and a better conductor, I believe this is lead free.
150 pieces of shrink tubing - it shrinks to half its original size. You can use a hair dryer, lighter or match to shrink it.
The LED lights are diodes so power only flows in one direction. You will want to verify that the wires are connected with the correct polarity before soldering. You also want to be very careful not to touch the positive to the trailer frame or like you me you will be looking for the fuse that needs to be changed.
You can see the 16 gauge wire coming out of the front light grommet and where both sides connect to the LED strip in this picture.