Navigation Lights Explained

One of the most critical requirements for any vessel on the water is to have properly functioning navigation lighting.  Navigation lights aren’t just important for nighttime, either; they are also important safety features for times of reduced visibility. These lights are required by law, and they are considered the responsibility of the boat’s operator, so it is important that you are checking all of your navigation lights routinely to ensure they are operating properly.

Navigation lights are an important safety feature of your boat.  They can assist in preventing collisions, and they also provide important information about each vessel on the water.  Navigation lights inform those near the vessel about its size and direction.  This information is essential so that boaters can make appropriate decisions about how to navigate around nearby vessels.

There are several types of navigation lights and various requirements depending on the size of the vessel.  Navigation lights can vary by color, arc of illumination, range and position on the boat.  Understanding the requirements for navigation lights will help you to know what you need for your boat, but can also help you to better comprehend the activity of the boats on the water around you.  For the purposes of this article, we will be referring to the requirements for powerboats only.

Types of Navigation Lights

The all-around light, as its name might indicate, displays a white light in a 360-degree unbroken arc around the entire boat.  These lights should be visible from at least 2 miles away.  For small vessels (under 40 feet), an all-around light is required when traveling.  All boats should use their all-around light when engaged in trawling, diving or when anchored.

The side lights of a boat are two lights mounted on each side of the vessel.  On the port side, a red lamp should be used, and a green lamp should be used on the starboard side.  For vessels less than 65 feet in length, a single bi-color light can be used in place of the two separate lights, provided that it can be mounted in a position that meets the side light requirements. These lights show an arc of light approximately 112.5 degrees wide; the arc should start directly in front of the boat and reach to 22.5 degrees past the mounting of the light on the respective side.  For vessels less than 40 feet long, side lights must exhibit a range of 1 mile; larger vessels should have side lights with a visible range of 2 miles.  Side lights should always be in use when the vessel is traveling. 

The stern light should be mounted as close to the stern of the boat as possible, casting a white, 135-degree arc of light.  The light should be aimed so that the arc is cast evenly on both sides of the boat. The stern light must be visible from a range of 2 miles away.  The stern light should be used when the vessel is underway.

Masthead lights are white lights fixed over the fore and aft center line of the vessel that display a 225-degree arc around the front of the boat.  This effectively gives the masthead lights the same coverage as the side lights, reaching 22.5 degrees abaft the beam on each side. For boats under 40 feet in length, masthead lights should be visible from a range of 2 miles, while larger vessels should have masthead lights with a visible range of 3 miles.  Masthead lights should be used in combination with the stern light while the vessel is underway.

Powerboats on the Great Lakes can substitute an all-around light for the stern light and masthead lights during travel.  Similarly, boats under 40 feet in length can also substitute an all-around light for the stern and masthead lights.

While not required for most vessels, any boats conducting towing activities are required to display tow lights.  These lights are yellow in color, and are normally mounted above the stern light, casting a 135-degree arc that is shown evenly on both sides of the vessel.

If you own a sailboat, the regulations are a bit different, as sailboats under 65 feet in length do not require masthead lights.  Because of this, many sailboats are equipped with one tri-color light which combines the functions of the side lights and the stern light into one unit.  Sailboats should still use an all-around light when anchored or when trawling or diving.  Sailboats with engines should adopt the same regulations as powerboats.

With this knowledge about proper lighting, you should be able to safely navigate during nighttime or times of reduced visibility, and also better interpret the activity of the vessels on the water around you.  If you have any questions or need to replace a navigation light on your boat, please contact the experts at Marine Parts Source at (866)388-0390.