Navigation Lights and LED Upgrades

COLREGS Requirements — Arcs, Ranges, and the Law

Navigation lights are not optional equipment or a matter of personal preference — they are mandated by the International Regulations for Preventing Collisions at Sea (COLREGS), and every vessel from a kayak to a supertanker must display them correctly between sunset and sunrise, and in restricted visibility. The regulations specify not just which lights you must show, but their exact arc of visibility (the horizontal angle the light must cover), their minimum visibility range (how far away the light must be visible in clear conditions), and their color. Getting any of these wrong means your boat is not legally compliant, and more importantly, other vessels cannot identify your type, size, or heading — which is the entire point of the system.

The core lights for a sailing vessel under sail alone are: sidelights — a red light to port and a green light to starboard, each showing an unbroken arc of 112.5 degrees from dead ahead to 22.5 degrees abaft the beam on its respective side; and a stern light — a white light showing an unbroken arc of 135 degrees, centered on dead astern. Together, the two sidelights and the stern light cover a full 360 degrees around the vessel. A vessel under 20 meters may combine the sidelights and stern light into a single tricolor lantern at the masthead — a popular option on cruising sailboats because a single light at the top of the mast is visible at far greater distances than lights mounted at deck level.

When a sailing vessel is motoring (or motor-sailing), it becomes a power-driven vessel under COLREGS and must display a masthead light (also called a steaming light) — a white light showing a 225-degree arc from dead ahead to 22.5 degrees abaft the beam on each side — in addition to sidelights and a stern light. Note that a tricolor lantern must not be used when motoring; it replaces the sidelights and stern light only when under sail alone. At anchor, a vessel must display an all-round white light visible for 360 degrees. Vessels under 50 meters need one anchor light; vessels 50 meters and over need two (fore and aft).

Visibility ranges depend on vessel length. For vessels under 12 meters, the masthead light must be visible at 2 nautical miles, sidelights at 1 mile, and the stern light at 2 miles. For vessels 12 to 20 meters, the masthead light must reach 3 miles, sidelights 2 miles, and the stern light 2 miles. For vessels 20 to 50 meters, the masthead light increases to 5 miles, sidelights to 2 miles, and the stern light to 2 miles. These are minimums in clear atmospheric conditions — if your lights are dim, corroded, or partially obscured, you may be technically non-compliant even if they still illuminate.

Light Configurations by Vessel Type and Size

The lights you need depend on what your boat is doing and how big it is. Most sailing vessel owners need to know four configurations: under sail alone, under power (or motor-sailing), at anchor, and the optional configurations for vessels under 7 meters. Getting these right is not complicated, but mixing them up can create genuinely dangerous situations — especially in busy shipping lanes where commercial traffic is making split-second decisions based on your light display.

Under sail alone, vessel under 20 meters: you have two legal options. Option one is the tricolor masthead lantern — a single fixture at the top of the mast that combines red, green, and white sectors in the correct arcs. This is the preferred configuration for offshore sailing because the light's elevation makes it visible at greater distances and keeps it above wave crests. Option two is separate sidelights and stern light mounted at deck level — typically sidelights on the bow pulpit or shroud bases, and a stern light on the pushpit or transom. Deck-level lights are harder for other vessels to see in rough seas but are required when motoring (you cannot use the tricolor under power).

Under power (motor-sailing counts), vessel under 20 meters: display a steaming light (white, 225 degrees, mounted on the mast below the tricolor), sidelights (at deck level), and a stern light (at deck level). The steaming light tells other vessels you are a power-driven vessel. Many cruising boats have a single switch that activates the steaming light plus deck-level sidelights and stern light together — labelled "running lights" or "steaming" on the electrical panel.

At anchor: display an all-round white anchor light (360 degrees) where it can best be seen — typically at the masthead or on a staff on the foredeck. Many boats use the masthead tricolor fixture's white sector for this, but check that your tricolor actually provides a 360-degree white mode; some older models only produce the sectored red/green/white and do not have a separate all-round white function. If yours doesn't, you need a separate anchor light.

Vessels under 7 meters (dinghies, tenders, small daysailers) operating in areas where they are unlikely to encounter other traffic need only have available a white light (a flashlight or electric lantern) that can be displayed in sufficient time to prevent collision. This is the COLREGS minimum for the smallest vessels, but it is a minimum — if you sail a small boat in any area with traffic, proper sidelights and a stern light are far safer.

LED Conversions — Benefits, Pitfalls, and COLREGS Compliance

Replacing incandescent navigation light bulbs with LED equivalents is one of the most popular electrical upgrades on cruising sailboats, and for good reason: LEDs draw roughly 90% less current than equivalent incandescent bulbs, they last 50,000+ hours versus 1,000–2,000 hours for incandescent, they produce less heat (reducing fire risk in enclosed fixtures), and they reach full brightness instantly. For a cruising boat managing a limited battery bank, reducing the navigation light load from 3–5 amps to 0.3–0.5 amps is significant — it can mean the difference between running lights all night and waking up to a dead battery.

The problem is compliance. COLREGS specifies not just brightness but color chromaticity — the exact shade of red, green, and white that navigation lights must produce, defined by CIE chromaticity coordinates. Cheap LED replacement bulbs — the $5 units from marine discount websites — often produce colors that fall outside the COLREGS specification. A green LED that's slightly blue-shifted may look fine to your eye but can be confused with a white light at distance. A red LED that leans toward orange may not be distinguishable from a yellow towing light. White LEDs that are too blue (high color temperature) don't match the warm white specified by COLREGS and may appear as a different signal.

Visibility range is the other compliance issue. COLREGS specifies minimum visibility distances, and these are tested with specific photometric standards. An incandescent bulb produces light in all directions; a reflector and lens in the fixture shape it into the correct arc. LED bulbs have inherently directional light output, and a drop-in LED replacement may not illuminate the fixture's optics the same way the original incandescent bulb did. The result can be a light that appears bright when viewed head-on but falls below the minimum visibility at the edges of its required arc. This is particularly problematic in tricolor lanterns, where the internal optics are designed for a specific bulb geometry.

The right approach: either replace the entire fixture with a purpose-built LED navigation light that has been USCG-certified (look for the certification number on the fixture — it will reference 33 CFR 183.810 or the equivalent international standard), or use LED replacement bulbs from reputable manufacturers (Hella Marine, Lopolight, Aqua Signal, Dr. LED) that are specifically designed and tested for navigation light use. Avoid generic automotive LED bulbs and unmarked imports. The cost difference between a $5 non-compliant LED and a $25 compliant one is trivial compared to the consequences of not being seen at night.

Wiring Runs to the Masthead — Voltage Drop on Long Circuits

The masthead of a sailboat is typically 50 to 65 feet from the electrical panel, and the wire must run up inside the mast, creating one of the longest single circuit runs on the boat. This distance creates a problem that does not exist for circuits closer to the panel: voltage drop. Every wire has resistance, and that resistance increases with length and decreases with wire cross-section (gauge). On a 12-volt system, even small voltage drops are significant — a 10% drop on a 12V circuit means only 10.8V reaches the light, which can reduce incandescent bulb output by 30% or more and may cause LED drivers to flicker or shut down entirely.

Calculate voltage drop before choosing wire gauge. The formula is straightforward: voltage drop = (current in amps x total wire length in feet x 2 for round trip x wire resistance per foot). For a tricolor drawing 1.5A on a 60-foot mast with 16 AWG wire (4.02 ohms per 1,000 feet), the drop is 1.5 x 120 x 0.00402 = 0.72 volts, or about 6% on a 12V system. That's acceptable. But an older incandescent tricolor drawing 3.5A on the same wire drops 1.69 volts — 14%, which is above the 10% maximum recommended for navigation lighting and the 3% recommended by ABYC for critical circuits. This is why many boats with original wiring have dim masthead lights — the wire was sized for the original load but barely, and corrosion has added further resistance over the years.

The solution for new installations is to use the largest gauge wire that will fit through the mast conduit, and to use tinned marine-grade wire exclusively. For LED loads, 16 AWG tinned wire is usually adequate for masts up to 65 feet, but 14 AWG provides a margin for future additions (VHF antenna coax and Windex wiring often share the conduit). For incandescent loads or mixed circuits with a masthead anchor light, 12 AWG is preferred. Never use solid-core household wire — it work-hardens from mast vibration and fractures within a few seasons.

The mast base connector is the single most failure-prone point in the entire masthead lighting circuit. Where the wires exit the mast and connect to the boat's wiring, there is almost always a multi-pin plug or terminal block that is exposed to water running down the mast, salt spray, and condensation. Corrosion at this connection is responsible for more masthead lighting failures than all other causes combined. We'll cover this in the troubleshooting section.

Troubleshooting Dim, Flickering, and Non-Working Lights

Navigation light problems fall into three categories: dim lights (the light works but is not as bright as it should be), flickering or intermittent lights (the light works sometimes, or flickers with vibration or heel), and dead lights (no output at all). Each has a systematic diagnostic path, and in nearly every case, the root cause is corrosion at a connection somewhere in the circuit — not a failed bulb or a bad switch. The marine environment is relentless, and any connection that is exposed to moisture will eventually develop enough resistance to degrade or interrupt the circuit.

Dim lights are almost always caused by voltage drop from corroded connections or undersized wire. Start at the light fixture and work backward toward the panel. Measure voltage at the fixture terminals with the light on — you should see within 0.5V of battery voltage. If you're reading 10.5V at a fixture on a 12.8V system, you've lost 2.3V somewhere in the circuit. Now measure at the mast base connector — if you see 12.5V there but 10.5V at the fixture, the problem is in the mast wiring or the masthead connection. If you see 11.0V at the mast base, the problem is between the panel and the mast. Divide and conquer — check voltage at every accessible connection point to isolate the section with the highest drop.

Flickering lights point to a connection that is making and breaking contact — a loose terminal, a cracked solder joint, or corrosion that creates a resistive contact which opens under vibration or thermal expansion. The most common locations are the mast base plug (which sees constant vibration and water), the masthead fixture wiring connections (exposed to UV and moisture for years), and the deck-level sidelight connections (often buried behind trim and never inspected). Wiggle each connection while watching the light — when the flickering changes, you've found the problem.

Dead lights require verifying power at the panel breaker first. If the breaker has power out, trace the circuit connection by connection. A multimeter set to continuity mode with the circuit de-energized is your best tool — disconnect the wire at both ends and check for continuity through the conductor. No continuity means a broken wire, usually at a connector or where the wire passes through a sharp-edged hole in the mast or deck. On boats over 15 years old, the most common failure point is the mast base multi-pin connector, where corrosion has built up enough to completely open the circuit. Disassemble it, clean the pins with fine emery cloth, apply dielectric grease, and reassemble.

Installing New Navigation Light Fixtures

Whether you're replacing corroded fixtures with modern LED units or upgrading an older boat that never had proper lighting, installing new navigation light fixtures is a straightforward job — but the details matter for longevity and compliance. Fixture selection comes first: choose USCG-certified fixtures from established marine manufacturers (Hella Marine, Aqua Signal, Lopolight, Perko). Verify the fixture meets the arc and visibility requirements for your vessel size. For deck-level sidelights, verify the fixture's mounting position will provide an unobstructed arc from dead ahead to 22.5 degrees abaft the beam — bow pulpit mounts are ideal but must not be blocked by furled headsails, anchor gear, or lifeline stanchions.

Mounting requires proper backing and sealing. Sidelights on the bow pulpit or cabin sides need a flat, solid mounting surface. If mounting to fibreglass, use a backing plate (stainless steel or G10) on the inside to distribute the load and prevent the screws from pulling through. Bed the fixture base in polyurethane sealant (3M 4200 or equivalent) — not silicone, which does not adhere well to most light housings and will crack over time. For masthead fixtures, the mounting surface is the masthead plate, which is typically pre-drilled for the fixture; match the screw pattern exactly and use stainless steel fasteners with Tef-Gel or Lanocil on the threads to prevent galvanic corrosion between stainless fasteners and aluminium mast.

Wiring connections at the fixture must be waterproof, period. Use heat-shrink solder connectors or adhesive-lined heat shrink over soldered joints. Do not use crimp connectors with vinyl insulation for any exterior or masthead connection — they wick moisture into the crimp and corrode within two seasons. Where the wire enters the fixture housing, ensure there is a drip loop — a downward loop in the wire below the entry point that prevents water from running along the wire and into the fixture. Many fixture manufacturers provide a rubber grommet or cable gland for the wire entry; use it, and apply a bead of sealant around it.

After installation, test every light not just for function but for correct arc coverage. With the boat at the dock, walk the dock (or row a dinghy) and verify that each light turns on and off at the correct bearing relative to the vessel's centerline. The sidelight transition — where the red becomes invisible and the green appears (or vice versa, looking from astern forward) — should occur at dead ahead, with no visible gap or overlap. The stern light should be visible from dead astern to 22.5 degrees abaft the beam on each side, meeting the sidelights' cutoff. Any gaps in coverage mean a vessel approaching from that angle cannot see any light — and that's how collisions happen.

1. Select and verify fixtures

   Choose USCG-certified LED fixtures rated for your vessel's size class. Verify arc coverage (112.5 degrees for sidelights, 135 degrees for stern, 225 degrees for steaming, 360 degrees for anchor) and minimum visibility range. Confirm the mounting pattern matches your existing holes or plan new mounting locations.

2. Prepare mounting surfaces

   Clean the mounting surface thoroughly. For fibreglass, lightly sand with 220-grit to provide a key for the sealant. Install a backing plate on the interior side if mounting through thin fibreglass or if the screws will be load-bearing. Dry-fit the fixture and mark screw holes.

3. Drill and seal

   Drill screw holes slightly undersized. For fibreglass, seal the raw edges of each hole with unthickened epoxy to prevent water intrusion into the laminate. Apply a generous bed of polyurethane sealant to the fixture base and set it in place. Tighten screws evenly but do not over-torque — you want sealant to squeeze out evenly around the entire perimeter.

4. Wire the fixture

   Run tinned marine-grade wire from the fixture to the nearest junction point or directly to the electrical panel. Leave a drip loop below the fixture's wire entry point. Make all connections with heat-shrink solder connectors. Apply dielectric grease to any plug-in connectors. Verify polarity — reverse polarity will not damage most LED fixtures but the light won't work.

5. Test and verify

   Turn on each light individually and verify function. Check current draw with a clamp meter or multimeter at the panel — compare to the fixture manufacturer's specification. At night, verify arc coverage and color from the dock or a dinghy. Confirm no double-lighting conflicts between tricolor and deck-level lights.