I have a 1999 Merc 200 Bluewater series with carbs, and I was wondering, what is the most volts it should charge ? When trolling it is right on 12-12.5 volts. When running, sometimes it will go as high as 15.9-16.1. Is this normal ? I run plotter, 2nd gps, vhf, sounder, and sometimes stereo. Also, I do not know RPM's as the tach has not worked since buying the boat 1 1/2 years ago. I am thinking the two may be related as I know the tach gets its feed from one of the two voltage regulators. Thanks in advance.