What to do with the extra wire

[thesaintlyone]

If you don't plan sailing at night until after the winter, just ignore them and sort out when you have the mast down. much easier to see what is going on then, and you will probably want to rewire the mast anyway. Even if you do need nav lights, presumably you have deck level lights as well.

TBH that is probably the best bet I'm only gonna be doing local day sails maybe a couple of anchors but arriving i plenty of time just to get used to the boat I do have Deck level LED nav lights and I can buy an anchor light to hang or stick on a pole

 

[PowerSlapper]

My mast head wiring consists of 2 nos 3 core cables. One cable feeds the mast head tricolour and anchor light. one core is for tricolour, one core is for anchor light and the third core is a common neutral.
The mast mounted steaming light and deck light are fed by the other cable and again with a similar setup. One core for the steaming light, one core for the deck light and the remaining core is a common neutral.
The two cables (6 cores) go through deck glands and terminate in a box below deck. The two neutrals are joined together and are connected to the -ve bus behind the main switch panel. The remaining 4 cores are connected to the appropriate switches on the main switch panel (Anchor, nav1, Steaming and Dec). The easiest way to sort out which "pair" is which is meter the pairs to find which pair has highest resistance, the third core will be the common neutral. To determine which of the remaining leads supplies which light, simply connect a 12v supply between each of the remaining leads and the common neutral in turn and see which light lights. Repeat for the other cable and Bob is your father's brother.

 

[Spirit (of Glenans)]

On both my Benes the mast lights were fed by what looked like house hold 3 core. They used two positives and a common negative.
Stu

I had a UFO 27 that had both the pulpit and pushpit nav lights and the masthead ones wired like that, using domestic 2.5 sq.mm T+E, obviously using such seemingly heavy cable to reduce the voltage drop over long runs. Up the mast, one colour went from the switchboard to the "positive" side of each lampholder, and the "Earth" connected the "negative" side back to the busbar.