2015 Etec E30DPSLADF 05441880 2 1/2 years old, 140 hrs on a flyfishng Micro Skiff single battery for start and 12V trolling motor. I have GPS which displays voltage. All worked flawlessly: run out in morning displayed 14.2V, run, troll, charge all day, voltage varies, but on the run charges up from 12,2-7 to mid 13’s. On run Home would gradually charge up to high 13V. Always very stable. Last three times out, all of a sudden voltage on the run would vary often and quite a bit. Thought it was battery, put in new battery, last trip on way home voltage varied fro, 12.5 or 12.6 to 13.1, then back and forth. Bad alternator or V regulator? All accessories on accessory panel. Advice appreciated.