I think found PART of the problem

[Captain Smollett]

My steaming light has not worked since I've owned the boat.  I've replaced the light fixture and bulb, cleaned the contacts at the through-deck plug and checked voltages/continuity at the plug and the light fixture itself.  It still did not work.  My threory was that was just enough resistive loss in the circuit to not light the lamp, but not enough to show on my ohm meter (which is only sensitive to kilo-ohms)

So, I decided to run new wire.  Today, while stripping the old wire out, I found a splice a few inches down from where the wire went out of the mast at the light end.  The ends were soldered together, but there was no covering on the splice - just bare wire.  The exposed splice was very corroded.

I'm hoping that was the source of the problem; at the very least it could not have helped the light work reliably.  I don't know if this was a PO trick, or done at the factory.  Either way, I cannot believe somebody left a bare splice inside the mast.

[AdriftAtSea]

I hope that wasn't the hot wire... Good thing you found it.

[Captain Smollett]

Yes, it was both wires.   

[CapnK]

John -

So, for the new light, all you had to do was solder the wires to the mast.... Cool!