When the Boat center rigged my last boat, they went with 10ga marine. This is two wires in sheath. I would only buy marine wire, and probably run the 10ga for best performance. It will probably start up with 14, run good with 12, but never have a lack of performance concern with 10ga. Some will say 14 or 12 GA is good enough, but when 10ga is advertised for less than $1.25 a foot, you would only save pennies by doing so. I had larger locators though, with a higher Amp draw, you could probably get away with whatever you want, but wire is cheap.