Boat Navigation Lights

Boat Navigation Lights are essential for boating at night. There are rules to follow when installing Navigation Lights. The are governed by the Coats guard and ultimately the IMO or International maritime Organization. If stopped by the Coast Guard you will need to demonstrate that these are working correctly.

These navigation lights to the right are a bit old, but they are not so outdated. The basic lamp has a housing with a bulb inside and a colored lens to give red, green or white light spread over an arc.

This basic design has been used for a long time, but what has changed is the technology. Light fixtures are smaller and more waterproof. Now we find LED clusters sealed into a very robust housing that are virtually bullet proof. The low current draw, maintenance free, long lasting, but expensive LEDs are small and bright.

International Navigation Light Rules

International Regulations for Preventing Collisions

US Navigation light rules

Range of Visibility

For the full description of the US rules regarding navigation lights see USCG RULE 21 DEFINITIONS. The outline is shown below. Navigation lights for boats include, anchor light, masthead lights, and running lights; stern light, & bow lights.

The lights prescribed in these Rules shall have an intensity as specified in Section 8 so as to be visible at the following minimum ranges:

(a) In vessels of 50 meters or more in length:

  • a masthead light, 6 miles;
  • a sidelight, 3 miles;
  • a towing light, 3 miles;
  • a white red, green or yellow all-round light, 3 miles.
  • a special flashing light, 2 miles.
  • (b) In vessels of 12 meters (40 ft) or more in length but less than 50 meters in length;
  • a masthead light, 5 miles; except that where the length of the vessel is less than 20 meters, 3 miles;
  • a sidelight, 2 miles;
  • a sternlight, 2 miles;
  • a towing light, 2 miles;
  • a white, red, green or yellow all-round light, 2 miles.
  • a special flashing light, 2 miles.
  • (c) In vessels of less than 12 meters (40 ft) in length:
  • a masthead light, 2 miles;
  • a sidelight, 1 miles;
  • a towing light, 2 miles;
  • a white red, green or yellow all-round light, 2 miles.
  • a special flashing light, 2 miles. The arc of visibility from the USCG below shows the range and arc and color of the various lights required.
  • Navigation Light Rules are slightly different for inland waterways. See USCG regulations rule 20-29 govern lights


Navigation light layout

Bow, Stern, and Masthead lights


The 360 degrees around a boat are divided up into 3 quadrants; Port, Starboard and Stern. This the arc of the port nav light

USCG Definition of lights; Masthead, side and stern lights



Navigation Light placement

Tricolor or Deck

The question for sailboats and powerboats with masts is should I have a tricolor light on the masthead or have separate port, starboard and stern lights mounted on the deck.

There are pros and cons to both a single light and 3 separate lights. Some boats have both with a sliding switch that lets you choose the tricolor or the deck lights. This way if you want the range and visibility in waves use the tricolor and if you have a problem with the tricolor you can switch back. This redundancy is a safety issue.

Tricolor pros

  • Better visibility
  • Better range
  • Only one light to maintain

Tricolor Cons

  • Reliability If a bulb goes or you have a wiring problem you may not be able to see
  • Maintenance to fix you need to go up the mast


Navigation Light Bulb types

  • Tungsten bulbs. Tungsten bulbs have been on boats for ever. they offer a warm glow. Typically the tungsten bulb is a high current draw and put of a lot of heat. they do not last long but are cheap .
  • Halogen Bulbs. Halogens are more efficient than the standard tungsten bulb and they last longer. they also put off a lot of heat if not hot.
  • Fluorescent bulbs. Fluorescent bulbs do not use as much energy and are not as hot, but they give off a cold light.
  • LED bulbs. LED bulbs have a low current draw and last a long time making them desirable onboard. LED ar becoming more in vogue as the light output is becoming brighter and more colorful

LED Navigation lights

Should you change to LED?

Up until a year or so ago most navigation lights were incandescent. The early LEDs that came on the market promised low current draw but were still evolving. Now many of the new navigation lights on the market are LED.

If you still have incandescent navigation lights it’s time to upgrade to LEDs. Even if you replace just a few bulbs you will save energy, reduce maintenance, and have a robust bright light that will last a long time.

An LED is a Light emitting diode: a semiconductor component that radiates light when charged with an electric current. In this process, light is produced by electronic reactions inside the semi conductor. This process is called electroluminescence.

Incandescent bulbs turn less than 20 percent of the power they burn into light, and 80 percent is dissipated into heat. LEDs are the polar opposite and turn 80 percent of the power into light, and just 20 percent into heat

LEDs are very energy efficient and consume little power, with up to 90% lower amperage draw than incandescent bulbs. The 90 % savings in power is most appreciated by sailboats who chances are will not be running the engine at night. Replacement of a few incandescent bulbs with LEDs reduces the load on your electrical system including your battery and alternator.

The one problem is they are expensive.

Why change to LED?

Changing navigation lights to LED will reduce power consumption and reduce the chance of having to replace the bulb. LED lights are solid state and so are far more robust and shockproof than the filament of an incandescent bulb.

  LED Navigation Lights
Pros Low current draw
Cool to touch
Long lasting 50,000 hours
Solid state and shock resistant
Voltage regulated (driver) the LED will still put out its light output will low voltage.
Cons Expensive

LED Navigation light Drivers;

LED lights require a DC to DC driver to regulate the current from the power source which can be between say 10VDC to 30VDC. Some drivers are external to the bulb while others are integral. Integral drivers work best. LEDs can be dimmed without changing color.

Upgrading to LED light fixtures

LED navigation light fixtures include two basic types. They are sealed clusters of LEDs like the Lopolight or the more traditional design of a housing and lens combination with an internal bulb.

One of the features you find with LED navigation fixtures is that they can be sealed like the Lopolight. Since the life of the LED is so long there is no need to replace the bulb. Being sealed the fittings are completely watertight.

Upgrading to LED fixtures can give us a lot of benefits as seen above. Another of the benefits is the size. LED fixtures are smaller for the same range (i.e. 2 mile) than incandescent fixtures. The Lopolight fixture in the picture below has been installed in the old incandescent housing.

The most popular LED navigation lights currently on the market are the Lopolight, Orca green and Aqua Signal. There are more manufacturers, but these three are USCG certified.


Lopolight is a sealed housing containing a cluster of LEDs arranged by color. For the masthead tricolor light there are clusters of red green and white sealed into a machined aluminum housing. This makes for a very robust and small fixture as seen in the picture right of a port 2 mile Lopolight.

The Lopolight 2 mile masthead tricolor is around $500. 2 mile tricolor with anchor light $700

Hella Marine NaviLED

This image shows a Hella series 41 steaming light next to the new port and starboard compact NaviLED Navigation Lamps. This demonstrates the size difference, which makes mounting the fixtures a lot easier. Both are 2 mile USCG certified lights.

A series 41 tricolor light cost around $60 while the NaviLED equivalent cost around $600.

Orca Green marine

Orca green has a sealed machined housing. You can see the clear lens of the sealed Orca green marine masthead tricolor on the masthead right.

Description; LED Tricolor / Anchor combination light with photodiode to automatically turn anchor light off during daylight hours. US Coast Guard Approved for sailboats up to 65 feet. Five times less power than comparable incandescent Tricolors. New – Waterproof quick-disconnect… Cost around $439.

An interesting portable navigation light for small craft is the Intelight personal strobe

Upgrading to LED bulbs

Change your existing bulb to an LED bulb

If you do any upgrading and are not into the expense of new fixtures then bulb replacement is an option. If you have the original fixtures in good shape and the lenses are clear then bulb replacement is an option.

If you replace just the bulbs there is no reason to change the fixture or wiring assuming they are in good condition. This will save a lot of money and can be the best bang for the buck.

Replacing an incandescent bulb with an LED is a big step forward. This may not give you the full effect of an LED fixture but it will be close. Just replacing the bulb may take the fitting out of its Coast Guard approval. Also LED fixtures have heat sinks to help the LED operate in high temperatures. An incandescent fixture will not have this feature.

LED lights are color specific, i.e. they are red, green or white. So when you replace a starboard running light bulb make sure you pick the green replacement. With incandescent lights the bulbs are just white as the lens gives the color.

Companies producing replacement bulbs include DR LED, their USCG and COLREGs certified Polar star is designed to replace Aqua signals series 40 bulb. The cost of one bulb is around $50 so this is much more than a regular incandescent bulb. The Polar star tri is shown above right.

Yacht Lights has a range of LED bulbs to fit a variety of light fixtures

Dr LED has replacement bulbs

Other companies specializing in LED replacement bulbs include Imtra.

Boat Navigation Lights recognition

Interpreting Navigation Lights

At night you will see all sorts of lights on the horizon. Which of these are boats, which are ships, fishing vessels, barges and tows? Being able to interpret lights, makes it easier for you to know how to navigate around these vessels.

Your navigation lights help other boaters know what you are (40ft power boat for example), where you are and which direction you are moving. Now can you identify the other boats around you?


Weems & Plath Light rules

Another tool for help recognizing vessel lights and shapes are the Weems & Plath Light rules

This navigation light recognition device works like an old fashioned slide rule. Slide the main body of the LightRule until you see the lights you see on the horizon and then read what kind of boat you are looking at.