Check fuse first, then test for power at the socket, then check the ground. 70 percent of failures are bad ground or corroded socket.
Step 1 -- Check the fuse
Nav lights run on a dedicated circuit. Pull the fuse and inspect. A fuse that blows again immediately after replacement indicates a short circuit in the wiring.
Step 2 -- Test for power at the socket
With the nav light switch on, probe between the hot terminal and ground with a multimeter. Should read 12V+. No voltage means the break is upstream in the wiring.
Step 3 -- Check the ground connection
The most common failure is a corroded ground wire. Check both at the light and where it connects to the ground bus. Green corrosion on the terminal is the tell.
Step 4 -- Replace bulb or socket
If power and ground are confirmed good, replace the bulb. LED replacements are available for all marine nav light sockets and are strongly recommended -- 80 percent less power and 10-plus year service life.
Step 5 -- Test all positions
Test all required lights: red port, green starboard, white stern, white anchor. All must illuminate with no flicker before operating after dark.
Sources & methodology: Repair procedures verified against ABYC standards and outboard manufacturer documentation. Difficulty ratings and cost estimates reflect typical DIY conditions. All guides reviewed for accuracy. Our editorial standards.
Frequently asked questions
What nav lights are required on a pontoon?
For boats under 26 feet: red port sidelight, green starboard sidelight, and white stern light visible from dead aft through 135 degrees. An all-around white light may substitute on boats under 12 meters.
Can I use LED bulbs in marine nav lights?
Yes and strongly recommended. LEDs use far less power, last 10-plus years, and are less affected by vibration. Verify the replacement is USCG-certified for that specific light position.