Underwater lights

[PJHoffnet]

Our 'new to us' boat has two underwater lights - seen during survey haul out - and easily found when looking at the transom from inside the boat.

The lights appear to not work (turning rocker on helm on and off while dark outside).

Did not see excessive growth covering the lights during the haul out. So don't believe they're simply fouled.

My next step (next time I'm at the boat) will be to test voltage to the lights by removing the screw on 'cap' (#1 below) with wiring leading to the light (I don't believe this breaks a water tight boundary, but will certainly have spill protection ready and also be ready to screw it back on quickly.

If voltage check is ok, my next trouble shooting effort would be to check the lights themselves to ensure there's not an open in the filament (not sure if these are filament or LED).

It certainly appears that the hardware is set up to allow access to the light from inside the boat (#2 below). NOT SURE IF THIS BREAKS THE WATER TIGHT BOUNDARY or if the lens that covers the light is the boundary (which makes more sense in my mind since you don't want to get the bulb wet).

So question for those who have replaced uw lights before - can I do it wet, or need to wait for next time I'm on the hard?

[shrew]

Originally Posted by PJHoffnet

The lights appear to not work (turning rocker on helm on and off while dark outside).

Did you check to see if there is a breaker on the 12V panel for the underwater lights? Is there a breaker on the 12v panel for the helm where switch is located.

For example if I want to honk the horn at my upper station, I need to turn on the 12v panel main, then turn on the upper station breaker on the 12v panel, then turn the horn switch on at the upper station, then I can honk my horn. (WTF??)

[mrt214]

I would definitely check for breaker or fuse that blew. Is the light on at the rocker switch?
These thru hull lights are not cheap, so check everything leading up to the lights.

[mmwjr]

Those are big fixtures so not LED.

I would first check for power at the switch then check near the fixture but not by removing the nut you point out. Trace that cable back and find an easy point where you can cut open the outer jacket to access the wires then pierce the positive one to check for power. Once done seal it up with a liquid wire insulator.

[PJHoffnet]

Thanks to all for the good troubleshooting guidance. When I'm down at the boat next week I'll start cranking through them and post what I find.

[PJHoffnet]

Was doing some house cleaning on subscribed threads and found this one I left hanging.

So, first off I'm dumb ... no big surprise there. The switch on the helm I was using to try to turn on the underwater lights (labeled Docking Lights) obviously was the wrong switch. Foolish me thought that since I pull into my slip stern first, the docking lights would be those underwater lights on the stern!!! OK, I now know what docking lights are, and no, my boat doesn't have them. But hey, I now have a 'empty' switch on the helm I can hook something up to if needed. Eventually found the correct switch/power source - one of the breakers on my 12v panel, labeled accessory (and having a white switch vice red like all the rest), serves as the on/off for the lights. I'm guessing the PO or the OO installed the lights but failed to label the breaker on the panel.

I did access the lights from inside the boat by unscrewing the nut labeled #2 in the picture. Bulbs (12v 35W MT8 blue halogens) on both sides were burned out. I tried finding a Blue LED replacement but couldn't so I just replaced with the same bulb. Light was weak when I tested them, but cleaned the lenses when I pulled the boat to replace zincs and now it's ok.

Not as cool as I thought, but that's ok since I'm a pretty uncool guy myself.