1988 25 XP; the batteries do not seem to be getting charged as much as of late. With all 3 batts online - being charged by alternator- voltage at the Batt terminal of alt. is 13.7 volts. Seems a little low. Is this a unit that could be bench checked by an automotive access. shop in the fall? Bad diodes??
Do you have the wire harness upgrade? If not then that is probably your problem. If you have the amp gauge at the instrument panel then you have the old wire harness. The alternator runs all the way to the amp gauge than back to the batteries creating a significant voltage drop.
77 : For a stock 55 amp alternator with an internal regulator, 13.7 v is about right.
That's why many of us went to a Hi output alternator with a smart 3 stage voltage regulator. Now we could sock amps back into the batteries in the shortest period of engine running time!!! A thought
I have the harness upgrade with a voltmeter and I have verified that the wire goes directly to the batteries