Re: 2000 90hp Mercury 4 stroke not charging battery ??
The most common cause of charging system failures on an outboard is failure of the rectifier. In your case, you should have a combined rectifier/regulator unit.
As I'm typing this, I see your next post regarding swapping of battery cables. This is 99.9999999 percent guaranteed to 'smoke' the rectifier. The flow of current thru the diode pack is instantaneous and far exceeds the amperage capability of the sensitive electronic parts.
So, my recommendations below still stand, but obviously the cards are stacked against the rectifier being a "Survivor"!
"Check all the electrical connections for corrosion/damage, make sure the ground wire(s) are snug and in good condition.
You can check the resistance of the charging coil wires coming from the stator. I don't have those values in front of me, but typically they'll be very low (in the area of just ohms or tenths of ohms.) If you check the stator wires with a digital VOM and get an open circuit (no continuity i.e. infinite resistance), the stator's shot and must be replaced.
I'd bet more on the rectifier/regulator unit myself. But you really need to check stator before spending $$ on an expensive rectifier/reg. Pick up a cheap VOM from Sears or Rad Shack, it'll be more than adequate for some resistance checks."
I'd plan on replacing, heck you might pull it off the motor and find the back is blown out! But it'd still be a good idea to check the stator resistance, just to make sure the reverse-current didn't damage anything else.
HTH & give us an update when you fix the problem........ed
