Alternator Not Charging Enough

[Giles]

" I have a 1985 Johnson 40 and

" I have a 1985 Johnson 40 and I dont think the alternator is charging enough. I have chainged the rectifier and that wasn't the problem. Can someone explain to me the checking procedure for the rest of the charging system? The motor runs fine but my volt meter (new) shows only a small amount of charge, maby 1/2 volt, with the battery somewhat discharged but still able to start. The battery is new. I also checked charging with an amp-volt meter. Under this low battery condition, how much should the alternator put out? "

 

[jon]

" Giles.. the volt meter is a

" Giles.. the volt meter is a pretty poor way to measure how the charging system is doing. The problem with these outboards charging systems is that they just don't have much balls; at low RPM's they typically don't charge at all. Tops that is charging at is 20 amps, I think it's actually even less though (I think it's a 10); an automotive alternator will charge at 70+ amps. It also depends how close the volt meter is to the battery and how good the connection is, as this will effect voltage readings. My merc 115 brings the volt reading up about one volt (13 when running).

Jon "

 

[Giles]

" Thanks for the reply, Jon. A

" Thanks for the reply, Jon. As I stated, I checked the alternator with a Fluke-Multimeter, and the volts is like 12.70 with motor off. When the motor is running, at about 3,000 rpm., the fluke meter shows 12.90---13 volts. From what you have said, I guess this is normal.-- THANKS AGAIN--- "