Understanding Boat Navigation Lights
Chris Riley Updated on December 9, 2020. In nauticalknowhowby
Boat navigation lights are essential when you’re out on the water. They’re essential, but it’s easy to misunderstand their uses and correct placements.
If you don’t know the correct placement for your stern lights or know what type of navigation light you need on your mast, don’t worry: we’re here to help. Below, we’ve got an overview of everything you need to know about boat navigation lights: what type of navigation lights you need, where to put them, and why you need to use them.
So without further ado, let’s learn more about boat navigation lights.
What navigation lights are required on a boat?
The U.S. Coast Guard Navigation Rules, International-Inland encompasses lighting requirements for every description of watercraft. The information provided there is intended for powerboats and sailing vessels less than 20 meters. The various options are illustrated.
The U.S. Inland Rules apply inside the demarcation lines at the entrances to inlets, bays, rivers, etc. The demarcation lines are shown on coastal charts as magenta dashed lines. Once outside of the demarcation lines, International Rules apply.
Power boats less than 20 meters shall exhibit navigation lights as shown in Figure 1.
(Note: 2 masthead lights are optional for vessels under 50 meters. Vessels over 50 meters will display two masthead lights.)
Vessels of less than 12 meters in length, may show the lights in either Figure 1 or Figure 2.
Powerboats less than 7 meters whose maximum speed cannot exceed 7 knots may exhibit an all-round white light, and if practicable sidelights instead of the lights prescribed above, in international waters only.
Sailing Vessels and Vessels Under Oars
Sailing vessels less than 20 meters may exhibit the navigation lights shown in Figures 3 or 4.
Another option for sailboats is to use a single combination lamp at the top of the mast as shown in Figure 5.
Sailing vessels less than 7 meters may carry an electric torch or lit lantern showing a white light to be displayed in time to prevent collision (see Figure 6 – left picture).
If possible, the lights prescribed for sailing vessels less than 20 meters should be displayed.
Vessels under oars may display the lights prescribed for sailing vessels, but if not, must have ready at hand an electric torch or lighted lantern showing a white light to be displayed in time to prevent collision (see Figure 6 – right picture).
Small boats can benefit from using a temporary LED light with a suction cup attachment if permanent fixings aren’t possible.
Shapes and Lights
To alert other vessels of conditions that may be hazardous, there are requirements to display lights at night and shapes during the day.
Powered vessels and sailing vessels at anchor must display anchor lights. An anchor light for a boat less than 50 meters in length is an all-around white light visible for 2 miles exhibited where it can best be seen (see Figure 7).
Vessels at anchor shall exhibit forward where best seen, a ball shape (see Figure 8).
Vessels less than 7 meters are not required to display anchor lights or day shapes unless anchored in or near a narrow channel, fairway or anchorage, or where other vessels normally navigate.
Anchor lights are not required on vessels less than 20 meters, anchored in special anchorages in inland waters designated by the Secretary of Transportation.
Sailing Vessels Under Power
Vessels under sail also being propelled by machinery, must exhibit forward where best seen, a conical shape with the apex pointing down (see Figure 9).
Vessels less than 12 meters are not required to exhibit the dayshape in inland waters.
Sailing vessels operating under machinery, or under sail and machinery are considered as powered boats and must display the lights prescribed for a power-driven vessel.
The Navigation Rules require vessels restricted in their ability to maneuver to display appropriate day shapes or lights. To meet this requirement, recreational vessels engaged in diving activities may exhibit a rigid replica of the international code flag “A” not less than one meter in height or at night display the navigation lights shown in Figure 10.
This requirement does not affect the use of a red and white divers flag which may be required by state or local law to mark a diver’s location. The “A” flag is a navigation signal indicating the vessel’s restricted maneuverability and does not pertain to the diver.
Navigation lights should be checked prior to departing the dock and you should always carry spare bulbs. The USCG doesn’t care if they were working when you left, only that they are working when required.
Where do navigation lights go on a boat?
The current navigation light requirements are found in the Navigation Rules, International-Inland, and in Parts 81, 84, and 89 of Title 33, Code of Federal Regulations. They’re easy to find, but many sailors and boat manufacturers do not have a good understanding of the rules governing the proper installation of navigation lights. To help clear up any misunderstandings here’s all you need to know:
Sidelights that meet the rules are designed to cover an arc of the horizon, or sector, of 112.5 degrees. Intensities are required to attain a visible range of 1 mile for vessels less than 12 meters (39.4 ft.) and 2 miles for vessels 12 meters or longer. These fixtures are designed for intensities to decrease and reach practical cutoff between 1 and 3 degrees outside their prescribed sector. Any side lights must be installed parallel with the fore and aft centreline of the boat and arranged to show an unbroken light from right ahead to 22.5 degrees abaft the beam, a total sector arc of 112.5 degrees.
Sidelights that are installed in the contour of the bow without providing a mounting surface tooled to be parallel with the fore and aft centreline of the boat are not in compliance with the Inland or International Navigation Rules. Depending on the breadth of the boat near the bow and how far aft from the vessel’s stem the lights are mounted, this shift can be more than 20 degrees in some cases. Installing the fixtures too far aft of the vessel’s stem may result in the sidelights not being visible from a position dead ahead.
Another factor in the proper installation of sidelights is that they must maintain their required minimum intensity in a vertical sector from 5 degrees above to 5 degrees below the horizontal. They must also maintain at least 60 percent of their minimum required intensity from 7.5 degrees above to 7.5 degrees below the horizontal. Installing flush-mounted sidelights, designed to be mounted to a vertical surface in the hull contour, without providing a mounting surface tooled to be vertical, shifts the vertical coverage sector. This also results in non-compliance with the Inland or International Navigation Rules.
Additionally, most of these flush-mounted sidelights are installed below the vessel’s rub rail. International Navigation Rules require that sidelights be installed above the uppermost continuous deck. Therefore, this configuration would not be in compliance with International Navigation Rules.
When separate red and green sidelight fixtures are used, the masthead light or all-round white light, whichever configuration is installed, must be located as close as practical to the vessel’s fore and aft centerline. For vessels less than 12 meters in length, the masthead light or round lights may be displaced from the fore and aft centerline providing that the sidelights are contained within a common fixture and mounted on the vessel’s fore and aft centerline. The masthead or round lights must be installed at least one meter (3.3 ft.) above the sidelights.
Which navigation lights are you required to display when anchoring your boat for the night?
Boating at night (or in reduced visibility) can present some special challenges. Not only is your depth perception lessened, but bright lights on the shore can also cast misleading reflections on the water and if you wear glasses, or worse yet bifocals, you simply don’t see as well at night as you do during the day.
It is not only important that you be able to identify other vessels operating in your proximity, it is equally important that other vessels see you. Most recreational vessels are less than 30 feet in length and, according to the Rules of the Road, shall be equipped with navigation lights.
These lights not only have a certain arc through which they can be seen but must be seen from a minimum distance. The following lighting requirements are for recreational vessels less than 12 meters in length. (approximately 39.4′)
|Starboard Side Light||112.5º||Green||1|
|Port Side Light||112.5º||Red||1|
The arc of the lights and color allows you to determine the direction a boat is moving. How good are your boat’s lights? You should test them to check your nighttime visibility, or you might land yourself in hot water with the Coast Guard.
Whether on a trailer or at the marina, switch on your lights and see how well they can be seen. Walk away from the boat or row away, if you are at anchor or at a mooring, and see how visible the lights are as you move further away. How easy are they to see against the background of lights onshore?
Does your stern light shine dead astern over the required 135º arc or does it shine to one side or up or down? Can it be seen from the required 2 miles and why is that important? As an example, let’s say that your stern lights can only be seen for 1/2 mile. You are underway at 8 knots and a large ship is approaching at 15 knots. The ship is only 4 minutes away from a collision with you. By the time the ship “might” see you, identify the light, and decide on how to move, it is too late. A ship traveling at 15 knots may take miles to stop.
Look at the stern lights again, as you move from the stern toward the bow, does the stern light “disappear” as the sidelight “appears”? The stern light should disappear and sidelight appear at 22.5º abaft the beam. If you don’t see the green starboard sidelight or the red port side light when the stern light disappears there is a problem with the arc of one or all these lights. This means that if another boat were approaching you at the angle where no lights are seen there is an increased risk of collision.
If both the stern lights and side lights are seen brightly at the same time you still have a problem. A boat approaching won’t know whether they are overtaking or crossing and whether they should give-way or stand-on.
You should also check to make sure that your masthead light disappears at the same time each side lights disappear and they both disappear when the stern light appears.
Check your sidelights from dead ahead. You should see both red and green. However, by moving toward one side just 1-3º you should then see only one light. If you still see two lights, an approaching boat won’t be able to tell which direction you’re are going.
It is very important to be seen from a distance but also for an approaching boat to be able to determine your direction of travel.
When boating at night remember the following: “When two lights you see ahead, turn your helm and show your red”.
Robert Hogward on September 12, 2021
Thanks for writing this post. I can either place them on the exterior or interior for decorations. Placing them on the exterior side is helpful when I go fishing and indulging in other night activities in the water.
Dalton Bourne on July 26, 2022
We love the lights! We put lights from Seaponer on my Jon boat right above the water line and use them for night fishing! The amount of brightness it offers is an assurance of my boat’s being seen clearly during the night. At the same time, the LED lights don’t consume too much energy, leading to a life span of up to 50,000 hours.