Low Voltage Alarm: Mercury 225 Pro-XS 2 stroke

[mthurma4]

Had an issue with motor last weekend and would like some confirmation.
At the end of a 6 hour fishing morning, I got a 4-5 second beep when I got onto plane. Engine went into guardian mode. I have been noticing my voltage gauge is only reading 12v when running and maybe slightly less at idle and will drop lower if trimming. My battery is a 6 month old DIEHARD 31 agm. No previous issues with it. I know this is not the top of the line battery but it met standards. Engine started fine all day even after guardian mode.
Is this a sign of an alternator going down? Or any other suggestions?

Thanks!
Y’all have always been the best!

[DucksnBobs]

Same thing happened to me last summer. My ground wire at the alternator broke at the connector. Go through all your wiring closely. Guaranteed you have a loose one somewhere. Put the motor on muffs, at idle it was reading 13+v, before 11.9-12.1 but would start right up without any issues. Could be the alternator I suppose but I’d make sure wiring is all intact and perfect still.

[JOE54]

check fuses and fuse link as well as ^^^ all grnds on alt and engine ,could be failing alt also