Why You Need Power Distribution For Underwater Lights

Its a lot of light. But a lot of light is exactly what some boats need.

Yachts, sport fishing boats, dive boats. If your boat has an extra-wide beam or your livelihood depends on producing fish for clients you may need five or six underwater lights.

Of course, that many lights is a big investment. But it’s not just an investment in your boat, it’s also an investment in your future. After all, your yacht is an investment in the memories you make with your family. And in a similar fashion, a sportfishing boat or dive boat is an investment in your business. It makes today’s clients happy and brings in more clients tomorrow.

Protect Your Investment

As with all investments, you’ll want your underwater lights to be protected so that they provide years of service. That’s why you need the SCM-PD power distribution box.

Power Distribution for Underwater Lights

scm-pd power distribution for underwater lights
6 Light Power Box

The SCM-PD is a power distribution box for single color underwater boat lights. It provides a convenient and secure way to wire up to six underwater lights.

The SCM-PD protects your lights in several ways.

First, it mounts in a convenient location near the back of your boat. Because of this, wires runs stay short with less chance of voltage drop, chafing, or damage.

Second, the box is watertight. Even the wires going into the box are sealed to keep moisture out. As a result, your wiring stays dry and trouble-free!

Next, all wire connectors are color-coded to match the wires from the lights. Because of this, it is much less likely your lights will be wired backward.

Finally, each light gets its own fuse. You can be confident your lights are well protected. And if one of your lights ever stops working, troubleshooting will be much easier.

Ease of Installation

Installing underwater lights using an SCM-PD is faster and uses fewer materials than wiring your lights in parallel. Consequently, you save money on labor and material costs. Here’s how.

Wiring six underwater lights in parallel, through a relay, would require 19 crimped connections and 32 crimps.

  • 10 Step Down Butt Connectors
  • 3 Ring Connectors
  • 4 Female Spade Connectors

By comparison, wiring six underwater lights through an SCM-PD box requires 8 crimped connections and 8 crimps.

  • 5 Female Spade Connectors
  • 3 Ring Connectors

Each connection your installer doesn’t have to make reduces the amount of time it takes to install your lights. It also reduces the number of connectors, wire, and shrink tubing you have to buy.

How It Works

To start, mount the SCM-PD in a convenient location. It should be mounted near the back of the boat as close as possible to a fuse block or positive bus bar and a negative bus bar. If wired to a positive bus, an inline fuse at least twice the total amperage of all lights wired to the SCM-PD must be used.

Next, run the cables from the lights to the box. Trim the cables to length and insert them through the cable glands.

Then, trim back the wires and snap them into the matching color-coded terminals. Tighten down the cable glands and add a fuse sized to at least twice the rated amperage of the light.

After that, cut a length of appropriately sized ground wire long enough to reach from the box to a negative bus bar. Trim insulation from one end of the wire and insert it into the negative terminal. Screw the terminal down to secure the wire firmly in place. Crimp a ring terminal sized for the wire and bus bar screws to the other end of the wire. Attach it to the bus bar.

Sometimes a Switch is Not Enough

Now we need a way to supply power to the box and turn the lights on and off. The easiest way to do this would be to power the lights through the switch.

Unfortunately, most rocker switches are rated for only 20 amps. Far below what we need to power five or six powerful lights.

In addition, inrush current temporarily doubles the amperage flowing through a switch at startup. This means the switch needs to be able to handle at least twice the amperage of all the lights wired through the SCM-PD.

In other words, our 20 amp switch can only handle 10 amps worth of lights. Definitely not enough!

power distribution for underwater lights relay

We need a relay!

A relay is a remote switch. It uses a low amperage rocker switch at the helm to turn on a high amperage circuit that powers the SCM-PD. Relays are used in cars, trucks, and other machinery to control headlights, pumps, motors, and other electronics.

Relays Have Two Sides

The first side takes current from a switch and passes it through a coil.

The second side takes high amperage current from a fuse block or positive bus bar and sends it to the device you’re operating. In our case the SCM-PD.

Turning on the switch sends power through the coil. The coil creates a magnetic field that pulls contacts on the high amperage side of the relay closed. When the contacts closed power flows to the SCM-PD turning on the lights.

There are a couple of advantages to using a relay to power the SCM-PD.

First, relays are made in many different amperages. It’s easy to find a relay to match your power needs.

Second, most relays are designed to handle inrush current. There is no need to double the amperage of all the lights. Simply add together the amperage of all the lights and choose a relay with at least that much amperage.

single color boat lights & amperage

Recommended Relays
30A Relay: TE Connectivity 1-1904007-1
40A Relay: Panasonic CB1A-R-M-12V
50A Relay: TE Connectivity V23134J1052D642

Do You Need Power Distribution for Underwater Lights?

If you are installing five or six single color underwater lights you need the SCM-PD power distribution box. It keeps your wiring neat, dry, and trouble-free. In addition, your underwater lights take less time to install saving you money on labor and material costs.

The SCM-PD is not your only choice when it comes to power distribution for underwater boat lights. Shadow-Caster makes a full line of power distribution boxes to fit your needs.

  • SCM-PD-Relay-4 for up to 4 color-changing underwater boat lights.
  • SCM-PD+ for up to 6 color-changing underwater boat lights

Buy your SCM-PD today!