How to Upgrade Your Boat's Lighting to LED (and Keep Your Nav Lights Legal)

Walk the boat and list each light: where it is, what it does, the bulb base or fixture type, and which breaker or switch feeds it. Note any that are already LED. This is also a good moment to measure a circuit's current draw before and after, so you can see what you've saved.

For cabin, head, cockpit, step and courtesy lights you can use LED replacement bulbs that fit the existing base, or new LED fixtures.

• Pick bulbs and fixtures rated for the boat's full voltage range. Marine LEDs are often sold as "multivolt" (for example 10–30 V); avoid bulbs meant only for a steady household or car supply.
• Choose the color temperature you like. Warm white looks more like the old bulbs. Red or dual red/white lights in the cabin and at the helm help protect your night vision.
• Check the fit: many LED bulbs are longer or wider than the bulbs they replace.

With the circuit off, remove the old bulb, clean the socket contacts and fit the LED. Turn the circuit on. If an LED stays dark, try turning the bulb around or swapping the wires: many LEDs only work one way, so a dead-looking LED may just be reversed. If it flickers, check the socket contacts and the voltage at the fixture with your multimeter.

33 CFR 183.810 says a certified navigation light carries a permanent label, visible without taking the light apart, that shows:

• "USCG Approval 33 CFR 183.810"
• "MEETS" and the standard it was tested to (for recreational boats, normally ABYC A-16)
• "TESTED BY" and the name of the Coast Guard-listed lab
• the maker's name and model number
• its visibility in nautical miles
• the date it was tested
• the identification and specifications of the bulb used in the compliance test

Lights too small for that label must be marked "USCG" plus their range, for example "USCG 2nm", with the full details on the package.

Because the bulb is part of the certification, the straightforward way to go LED on navigation lights is a complete LED fixture that carries the USCG label and the right visibility rating for your boat's length. Use an LED bulb in an old fixture only if the fixture maker lists that bulb for that fixture. The Coast Guard's boating safety site warns that some replacement lighting doesn't meet certification requirements, and that LEDs, rope lights, underwater lights and decorative lighting can break the navigation light rules. Decorative colored lights should never show red or green where they could be mistaken for sidelights. See the navigation lights guide for what your boat needs and where.

Read the voltage range printed on each light and make sure it covers your system, charging voltage included. On a 24-volt boat, use lights rated for 24 V. Lumitec says two of its 12 V lights can be run in series on 24 V, but only do that with lights whose maker says it's allowed, because if one fails the other goes out too.

LEDs draw less current, so the existing wire is usually big enough. Inspect it anyway: replace green, stiff or brittle wire and any splices that sit low in the boat. Blue Sea Systems' wire chart treats navigation lights as a critical circuit that should lose no more than 3% of its voltage along the wire, so long runs to a masthead or bow light may need heavier wire than you'd think. Keep each circuit fused to protect its wire.

Water is the enemy of LED fixtures and their wiring:

• Use adhesive-lined heat-shrink crimp connectors on every joint. No tape, no household twist-on connectors.
• Leave a drip loop so water runs off the wire before it reaches the fixture.
• Seal the screw holes and wire holes of exterior fixtures with a marine sealant suited to your deck.
• Keep connections up high, away from bilge water and spray.

Many older dimmers don't work properly with LEDs. Use a dimmer that the light's maker approves, or lights with built-in dimming. Lumitec notes that PWM dimmers (the common electronic type) can cause noise on stereo speakers, and that all LED lights with switching power supplies create some electrical noise.

Be careful with accent and underwater lights. BoatUS warns that mood lighting which could be mistaken for a light the Navigation Rules require for another kind of vessel can bring fines, and that blue underwater LEDs can seem to flash in waves, looking like the flashing blue light only law enforcement may use. Keep accent lighting dim, low and out of the helmsman's eyes so it doesn't spoil night vision or the lookout. Mercury's underwater-lighting article adds that blue underwater lights are illegal in some areas for that reason, and quotes the Coast Guard's Safety Alert 10-15: decorative lights, underwater or along the rub rail, must not hide or change the look of your navigation lights or get in the way of keeping a lookout.

Underwater lights come as thru-hull fixtures (a large hole in the transom, usually brightest), surface-mount units (small holes for screws and the cord, on the transom, hull sides or trim tabs) and "no-drill" lights that thread into an existing hole such as the drain plug. Mercury suggests looking for a marine-grade housing and an IP67 or IP68 rating. Wipe them clean with a mild cleaner and a soft cloth (abrasives scratch the lens), check now and then for water inside the lens or corroded wiring, and take surface-mount or no-drill lights off for winter storage.

Lumitec's first fix for noise from its lights is to keep the light's power wire away from other wiring: don't bundle it with stereo, radio or antenna wires, and cross other bundles at right angles. Lumitec says this cures the noise in about 9 out of 10 cases. Its second suggestion is a relay placed close to the power source, with the switch only controlling the relay. Keep LED lights and their wiring as far as practical from your VHF antenna and its cable, especially masthead lights.

The Coast Guard's safety alert describes a simple check. Do it after any LED upgrade, with each group of LEDs:

1. Turn the LED lights off.
2. Tune the VHF to a quiet channel, such as channel 13.
3. Turn the squelch down until you hear noise.
4. Turn the squelch back up until the noise just goes quiet.
5. Turn the LED lights on.
6. If the radio now hisses, the LEDs have raised the noise floor and are likely reducing your VHF and AIS reception. If it stays quiet, they haven't.

Switch the lights on one at a time to find the culprit. Then try, in order: rerouting its wiring away from the antenna cable and other bundles, moving the light or the antenna farther apart, adding a filter recommended by the light's maker, or replacing it with a better-designed fixture. The Coast Guard asked mariners who find interference to report it to the Coast Guard Navigation Center (choose "Maritime Telecommunications") with the make and model of the lights and radio and the distance between them.

At dusk, turn on every light and walk around the boat: nav lights showing the right colors in the right directions, no glare at the helm, nothing flickering. Record what you changed, the fixture models and their current draw in your BoatMend log, and keep a spare nav light bulb or fixture aboard.