89 or 90 Evinrude/Johnson 120 HP professional series.

This motor is new to me, so we are still trying to figure out its quirks.  System voltage dropped to 11 volts on saturday regardless of whether we were under power or not to the point that we had a difficult time starting the engine.  Once the engine starts, it runs okay.  You would think ignition at WOT would take some serious AMPS away from the battery, but the voltage gaugae showed no drop past 11 volts which makes me think that the engine is powering ist own ignition.

But the battery is not charging at all it seems...

From what i understand so far, juice is generated by the stator underneath the flywheel. further goes to the rectifier or is it called voltage regulator? According to an outboard mechanic, starting cable and charging cable is the same thing so i am not missing any hookups.

Any ideas?

I heard you can;t disconnect the battery on these while the engine is running ot it will cook the regulator.  If so, how the heck do you test the proper rectifier output?

Gonna do a more precise test today with a different battery and a meter.  Fully charged battery should be around 13 volts.  Under power system voltage should reach 14.5 or so, correct?

I`m putting out about 14 volts under full power with my Merc 150.

I couldnt really test it under full power Czar.  But i measured the stator voltage and it came back at 1round 150v ac +/- depending on rpm. So stator is working.

From the stator, 4 yellow  high coltage wires go to the voltage regulator.  From there 6 sets of wires go to the distribution screw block. I measured 11.7 volts on both sides of the rectifier output. One side drives the ignition, the other drives the charging/onboard DC system.

Hooked up a meter at the battery, voltage will increase 0.01-0.02 volts while the engine is running, but not significantly enough to show charging flow.

So I yanked the battery alltogether.  Threw it on the charger. After 6 hours it stayed at 11.7 or so.  Verdict? I think a dead cell in the battery.

2.2 volts times 6 cells in the battry should amount to 13.2 to 13.6 volts for a fully charged battery.

Guess we will find out for sure the next time i take the boat out with a new battery this time around.

Your charging system should charge at the battery with the engine running around 2000 rpm's 12.8 - 14.3 roughly.

If your problem is not solved, please advise and i will give you some troubleshooting tips.

Thanks John, a new rectifier took care of all electrical gremlins.