Installing Underwater Transom Lights

There are several reasons for installing underwater lighting on your boat, or marine vehicle. Professional divers like underwater lights to give them a better view when night diving. Boaters who spend a lot of time in shallow waters use lights to enhance visibility of underwater obstacles. Anglers like underwater lights to attract fish in the early morning or late evening fishing hours. Most of the time, underwater lights are used simply to achieve a brilliant display of color when boating. Whatever your reason for installing underwater lights, you can install them quickly, and easily by yourself in a matter of minutes.

Wire Through Hull

Prepare the boat’s work surface. If the boat is in the water, remove it on a trailer or hoist. Clean the transom with warm soapy water. Rinse the area and dry it thoroughly.

Mark the spot on the transom (back wall of the boat) where you want the lights. Place the light against the area and use a pencil to mark where the screw holes will be.

Drill a hole just large enough to pass the lighting wire through. Insert the wire from the light into the hole and feed through to the inside of the hull. Apply a generous coat of marine grade sealant such as 3M 3500 to the last few inches of wire, and the entire back, and the rim of the light fixture and press against the transom.

Apply a generous amount of marine sealant to each stainless steel screw and drill or use a screwdriver to secure the light to the transom with the screws.

Light Through Hull

Begin with the boat out of the water as in the above scenario.

Mark the spot on the transom where you wish to place each light.

Drill a hole large enough to accommodate the through-hull light fixture.

Apply a generous amount of marine grade sealant such as 3M 5200 around the edges of the light, and place through the hull.

Attach locking bolt to the inside of the through-hull insert and secure tightly with wrench.

Attaching Wiring

Connect the wires of either type of lighting system to 18-guage wiring long enough to reach from the transom to the helm of the boat.

Insert an electrician’s snake from the circuit breaker panel through the boat’s sidewalls down to the transom and attach the 18-guage wiring.

Pull the snake back through the side wall of the boat, up to the panel with the wiring attached. Disconnect the wire from the electrician’s snake and attach to a circuit breaker to control the on/off function of the lights.

Tip

Lights can be attached to the circuit breakers on the helm panel, or inside the cabin of a cruiser at the general circuit breaker depending on your desire.

Warning

Always disconnect the battery power to the boat, as well as any external power sources before attempting to connect anything to the circuit breakers or boat’s power source.