How to Install Underwater Boat Lights

Drilling Holes For LED Boat Lights

Installing Underwater Boat Lights

Installing underwater boat lights is a reasonably straightforward project. It’s a job that can be done safely by many people who have experience working on boats. On the other hand, if you do not have experience working on boats, or are uneasy about drilling holes through your hull, then you should leave this to the professionals.

The American Boat and Yacht Council have a handy search tool on their website that allows you to find ABYC certified technicians in your area. Follow this link to find ABYC Certified Technicians near you. You can also do a search for “certified marine mechanics” with your zip code tacked on to the end to find qualified marine mechanics in your area.

In either case, this post will show you what it takes to install underwater boat lights. After your lights are installed read my post on how to wire underwater boat lights.

Choose Your Mounting Location

The first step is to decide where you want to mount your lights. The best mounting location is usually on the transom as low in the water as is possible. Also, separating the lights by at least three feet will give you the best light coverage across your transom.

Next, use a template to check to make sure the lights fit and to mark the location of the power cord hole. IMPORTANT! Do NOT mark the location of the screw holes at this time. You will use the light itself to mark the screw hole location.

Check inside of the boat to make sure there is room to feed the power cord through. You are also making sure you are not going to drill into anything important such as wiring or hoses. If in doubt, find a different location for your lights.

If everything looks OK you can drill the hole for the power cord.

Drilling Holes Through Fiberglass

The most nerve-wracking part of installing underwater led boat lights is drilling holes for the power cord and screws.

The scariest part of drilling through your hull is the possibility of cracking your gel coat. The installation instructions provided by Shadow-Caster recommend running the drill bit backward.

To help, I found this video that shows the most recommended way to drill through gel coat without cracking it.

Steps to Drilling Holes for LED Boat Lights

Once you have determined the location where you want to mount your LED underwater lights, you will need to drill a hole for the power cord. CAUTION! DRILL ONLY THE HOLE FOR THE POWER CORD AT THIS TIME. You will use the light to mark the location of the screw holes later.

Here are some tips on how to drill holes for LED boat lights in a fiberglass boat.

Tools You Will Need

  • Face Mask- 3M Tekk Protection N95 mask is a good choice.
  • Safety Goggles
  • Carbide Drill Bit
  • Protective clothing such as long sleeve shirt and pants.
  • Chamfering Drill Bit

Drilling Through Gel Coat

  1. Use a new, carbide/ diamond tip drill bit in reverse to drill through the gel coat. Gelcoat is usually about 1/16″ thick.
  2. Use a chamfering bit to smooth the edges of the hole.
  3. Once you have the gel coat countersunk you can switch your drill direction back to forward and finish drilling through the hull.

Mark and Drill Screw Holes

Once you have the holes drilled for the power cord you can mark and drill the holes for the screws.

First, mark how deep the holes for the screws need to be. Hold the drill bit and screw together with the tip of the bit against the head of the screw. Place a piece of tape on the drill bit just above the end of the screw. That is how deep you should drill.

It is important to use the proper sized drill bit for the screws. 9/64 is the correct size for #8 screws used by Shadow-Caster.

  1. Feed the power cord through the hole until the light is against the hull.
  2. Position the light how you want it then pull it out and place tape where the screw holes will be.
  3. Put the light back in place and mark the first screw hole on the tape.
  4. Pull the light out of the way and drill the first screw hole.
  5. Put the light back in place and tighten down the first screw.
  6. Now you can mark and drill the hole for the second screw.

Mount the Lights

Finally, you are ready to mount the lights.

  1. Place a bead of silicone caulk around the power cord hole and each screw hole.
  2. Fill the screw holes with caulk.
  3. Press the light into place, Insert the screws and tighten them down.

That’s it! Your lights are mounted. Now it is time to wire your lights.

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