What Underwater Transom Lights are Best for Your Boat?

That depends. Transom lights should be matched to your boat and the water you boat in. But most of all they should also make your boat more fun to use.

Let me explain.

Underwater transom lights should do four things.

  1. Give even light coverage across your transom.
  2. Shine deep into the water.
  3. Be reliable with little maintenance.
  4. Most of all, they should make your good times even better.
boat underwater lights and cockpit lights
Boat underwater lights should give even coverage across your transom.

Even Light Coverage

Underwater lights should create a pool of light across your entire transom. To do this they need to do three things.

  1. Flood the water with light. Some underwater lights produce a narrow beam of light, some a wide beam. A narrow beam gives a spotlight effect. A wide beam floods the water with light.
  2. Produce enough light, in lumens, to fill the space. As the space between lights increases, more light is needed to fill that space.
  3. Add more lights to fill in gaps where needed. When the space between lights becomes too large extra lights are needed to fill the gaps.
underwater boat lights
Outboard and sterndrive motors block light. Add extra lights for even coverage.

How Motors and Swim Platforms Affect Underwater Lighting

Outboard motors and stern drives block light and create shadows. This is not a problem on boats with a single motor. A light on either side of the motor cancels out the shadow. But boats with two or more motors are left with gaps in the pool of light.

The solution is to add more lights. On boats with two motors, one light should be placed between the motors and one on each side of them. This same pattern should be used on boats with triple or quad outboards.

underwater yacht lights
Underwater lights should be bright enough to shine past your swim platform.

Swim Platforms

Swim platforms cover the light from your underwater lights. Boats with wide swim platforms need more lumens. The pool of light they produce should extend at least a foot past the center of the platform.

Light travels farther in clear water.

Water Affects How Many Lumens You Need

Light travels farther through clear water than it does through dirty water. The dirtier the water you boat in the more lumens you need.

Of course, water clarity changes throughout the year. Water that is normally crystal clear can look like mud after heavy rains.

Throw out the extremes and think about how clear the water you boat in is during boating season. Is it clear, dirty, or somewhere in between?

If the water is more than moderately dirty you will need brighter lights to get good light penetration.

Freshwater vs. Saltwater

Quality underwater lights are made from either 316 stainless steel or bronze. Both stainless steel and bronze lights are good for freshwater or saltwater. The difference is that stainless steel allows marine growth while bronze prevents it.

If your boat is removed from the water after each use, you will be happy with stainless steel. On the other hand, if your boat stays in the water for months or years at a time, you should look for lights with bronze housing. This is especially important in saltwater where barnacles are a problem.

What’s Your Idea of Fun?

Boating is all about relaxing and having a good time. Whether it’s a night under the stars, overnighting in a secluded cove, or an overnight fishing trip, it’s all about fun.

Most boaters want enough light to make their boat look good. Others want their boat to stand out in a crowd. Still, others need enough light to attract fish from deep water.

To make your boat look good, think light coverage and water clarity. Start with enough light to give full coverage across your transom. If the water you boat in is dirty add more lumens to get better light penetration.

To outshine other boats simply add more lumens. But remember, boats with a narrow beam need fewer lumens to start with.

When picking underwater lights for fishing you need to think about water clarity and depth.

The minimum amount of light needed for waters under 30′ is the same as what you need to make your boat look good. Add more lumens in moderately dirty water or to draw fish in from farther away.

Even the sun only penetrates the ocean to around 656′. So if you fish deepwater you are going to need a maximum amount of light.

What to Look for in Underwater Lights

As I mentioned earlier, quality underwater lights have a housing made from either 316 stainless steel or bronze. The light housing must do three things.

  1. Resist corrosion, even in saltwater.
  2. Protect the light from damage.
  3. Transfer heat from the LEDs to the water. Cool LEDs shine brighter and last longer.

It’s What’s Inside That Counts

Boat underwater lights need to be protected from more than just the elements. Marine electrical systems can quickly destroy LEDs that are not protected. Three things can damage LED lights and cause them to fail prematurely.

Transient voltage spikes: Starting your motors, running your windlass, or even turning on a radio sends high voltage spikes through your boats electrical system. These spikes damage LEDs and cause them to fail prematurely.

Look for lights with electronics that block high voltage spikes.

Overheating: Underwater LED lights are cooled by the water. If left on out of the water they can overheat. Overheating damages the LEDs causing them to fail prematurely.

Look for lights with electronics that will reduce power to the light if it becomes too hot.

Reverse polarity: LEDs have a polarity. A direction current should flow through them. If the lights are wired backward current flows through them in the wrong direction. This can damage the LEDs.

Look for lights with electronics that prevent current from flowing in the wrong direction.

Underwater lights should complement your boat, where you boat, and how you use it. Boats with a wide beam or multiple motors need more lumens and more lights. Boating in dirty water or fishing for deepwater fish also requires more light.

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