what size of cable?

[nemodreams]

Bear in mind - when sorting out volt drop on masthead/long run stuff. Steaming, stern and bow combined etc are only used when the engine is running and you then have a 14.2 v supply which drastically alters volt drop calcs !

If I were 'under sail' at night I would use the tri. Making the anchor and tri led ( fit bulbs ) - will save current draw up there - so way less volt drop and leds are less fussy anyways than bulbs. Also - anchor and tri will never be used together - ditto Steam and deck flood - so negs can be shared.

I have one three core to mast top - one to spreaders.

 

[BabaYaga]

One further tip to the OP is to look at installation manuals for various equipment, where recommendations for cable sizes are often given.
An example: Raymarine Evolution autopilot, tiller drive. The installation manual states 2,5mm2 for cable runs up to 7m and 4mm2 for runs between 7 and 10m. NB this is not round trip, but total cable length from distribution panel to control unit to drive.