Inspecting Your Navigation Lights

 Is your boat ready for the night life?


by Frank Lanier
Southern Boating Magazine (2007)

When it comes to navigational lighting, “see and be seen” is a literal catch-phrase to live by.  Fully 30% of the vessels I inspect as a marine surveyor fail to comply with mandated navigational lighting requirements.  Many are owner induced deficiencies (from burned-out bulbs to installation of aftermarket equipment that blocks light fixtures) however a number of times I’ve seen navigation lights that were improperly installed by the manufacturer – many recreational boat builders either do not have a good understanding of the navigation rules governing proper installation of navigation lights or shoot for (and miss) the bare minimum requirements, often at the expense of the end user.

            The important thing to remember here is that regardless what the manufacturer did (or didn’t) do, when it comes to navigational lighting it’s your responsibility to ensure your boat complies with the rules.  Here’s how to verify you boat is ready for the nightlife.

The basics

            All boats must are required to display navigation lights between sunset and sunrise, during reduced or restricted visibility (fog, heavy rain, etc), or any other time deemed necessary by the operator.  Vessel’s 16 feet in length or greater must have properly installed, working navigation lights and an anchor light (which must be operable separate from the running lights).

            Required navigation light configurations are based on a number of factors, from vessel length, whether the vessel is under power or sail, as well as any special activity it’s engaged in (trawling, towing, etc). The type, arc and color of navigation lights allow boaters to determine a vessel’s size, propulsion (power or sail), if it’s anchored or moving, and if so it’s course.  For example, if you look over your bow and see a red light followed by a white light, you can assume the boat is crossing your path from starboard to port and (depending on distance) has the right of way – a single white light visible 360 degrees, on the other hand, would indicate an anchored vessel.

            The first step in determining if your vessel is compliant is to consult a copy of COMDTINST M16672.2D, also known as the Rules of the Road or the Nav Rules for short.  You can purchase a copy or view it for free online at  It’s beyond the scope of this article to list every possible configuration, however by way of example a typical powerboat less than 65 feet while underway at night or in reduced visibility would require side lights, a masthead light, and a stern light.  The side lights consist of a green light to starboard and a red light to port, both of which must cover an arc of the horizon (or sector) of 112.5° visible from dead ahead to 112.5° down each respective side.

            The masthead light is a forward facing white light on the vessel’s fore and aft centerline showing an unbroken arc of 225° and fixed to show the light from dead ahead to 22.5° abaft the beam on either side of the vessel.  The stern light, also a white light, must be visible from dead astern for an arc of 135 degrees (67.5° on either side of centerline).  You’ll notice that adding the arc of visibility of the masthead and stern light yields 360 degrees, which is what they’re shooting for visibility-wise – 360 degrees of white light visible no matter how you approach the vessel.  Vessels less than 39.4 feet in length have the option of exhibiting a single 360° white light in leu of a separate masthead and stern light. Finally, vessel’s anchored at night or in reduced visibility are required to display a single all around white light visible for 360°.

            Another important navigational lighting requirement is distance visibility, or how far they lights can be seen.  This is another case where meeting the letter of the law doesn’t necessarily mean the spirit of the law has been met.  I’ve seen installations that may meet the minimal requirements under perfect conditions (clear weather, minimal wave action, etc) but fail miserably in less than ideal conditions, the very times you want to make sure you’re seen.  Problems with regards to this range from poor location of the navigation lights (flush mounted sidelights in the hull below the rub rail are a good example of this) to the lights themselves, which are often too small or simply pieces of junk to begin with.

            To continue with our previous example (a powerboat under 65 feet in length) the masthead light must be visible for 3 miles, while the sidelights and stern light must be visible for 2 miles.  For vessels less than 12 meters (39.4) in length, required visibility of the masthead light is 2 miles and 1 mile for the sidelights.


            Once you’ve determined your vessel’s navigation lights meets the required configuration, next up is a physical inspection to determine everything is operating properly.  Start by turning on your running lights, then anchor light and verifying that each power up, can be operated separately, and meet the visibility requirements mentioned above (sailboat owners may find it easier to verify mast mounted anchor lights at night, when more easily seen than during the day).  Look for issues such as placement of equipment (lines, fenders, etc) that could block visibility, burned out bulbs, and poor lighting installations – a good example of the latter would be a masthead light that effectively blinds you when operating the vessel from the upper helm or fly bridge.

            Take a good look at the lights themselves – are they burning brightly or dim, a problem which can be caused by deterioration or “frosting” of the lens, installation of the wrong type of bulb, or a poor quality light – dirty lenses or corroded electrical contacts and switches can also cause problems. You’ll also want to verify that the side light lenses are correct (red port, green starboard) a problem I’ve seen where lights have been replaced by well meaning owners.  Once you’ve got everything in good working order, it’s a good idea to record the types of bulbs required for all navigation lighting and ensure you carry plenty of spares onboard.

            A simple approach to see how visible your vessel is at night is to turn on your navigation lights and walk away (or row a short distance if on a mooring) to see how visible they are as you move further away.  You should also check visibility of your navigation lights while underway – the stern on some smaller power boats “squat” while underway, which could cause a transom mounted stern light to be so low that it’s hidden by the boats own wake, a situation that could lead to being overrun by a following vessel.  Don’t be afraid to replace factory installed navigation lights with brighter, more robust units or relocate them to better comply with the Nav rules.  You also have the option of replacing incandescent lights with LED (light emitting diode) fixtures.  Modern LED units have numerous advantages, including long life (up to 100,000 hours in some cases), less power consumption, increased visibility, sealed construction (eliminating corrosion), and non-susceptibility to damage from shock or vibration.

            Finally, be sure to include checking the operation of all navigation lights as part of you pre-departure check list.  It only takes a moment and you’ll be doing yourself and everyone else on the water a favor.