1981 Mercury 50 HP 2-stroke:  charges my battery at 17.3 volts.  I replaced the regulator and the coil...same. same.  Should I just leave it or will it burn up the charging battery with time.z

17.3 reading on a multimeter? Maybe try a different battery and see if it does the same. And check the water levels in the battery (I always try the free stuff first )

My Garmin screen shows 12.5 volts while sitting and 17.3 volts when running full speed.  I like your idea...I'll put my multimeter on it too.

Your OB is charging the cranking battery...correct? The meter is connected to the OB alternate output.

Tom

18 hours ago, WRB said:

Your OB is charging the cranking battery...correct? The meter is connected to the OB alternate output.

Tom

Yes but I think that alternate output is supposed to be in the 14 v range

I don't know if the alternator has a current regulator in it to prevent batteries from cooking or it from cooking.

I wrote or emailed mercury with a question "can I rig up a system to charge both batteries on a 12/24v system without frying the alternator when I run the batteries way down"

The answer was "MAYBE", According to them it depends on the serial number.

I decided against it as we did it at work ( 24v mil. Comms) with a separate 24v alternator installed and we fried 3 (100 Amp draw from an inverter...don't ask, I know the numbers don't add up..let's say coffee was being made)

Drop Mercury a detailed email with the year, model, and s/n. They should be able to help.

Oh the system was some ganged switches to put the batteries in parallel and disconnect the trolling motor.

It was a 2005 merc 50hp 2 stroke

Fried 3 alternators and two military batteries exploded in the trucks bay once.