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Testing charging circuit on 1986 75 hp

Help! Have an 86 75 hp merc that is not charging the battery. What steps do I need to take. Have ordered a repair manual but not here yet.:)
 
Re: Testing charging circuit on 75

Use a volt meter and tell us what the voltage is on the battery at idle and at about 2500rpm. Make sure the battery is fully charged before you start. Fully charged battery should have 12.5 to 12.7 volts. I am just guessing here but the rectifier/regulator is probably shot but it could be the stator also. Let me know what the voltage is and we'll go from there.
 
Re: Testing charging circuit on 75

The battery voltage was 12.45 and decreased from there. I think the rectifier/regulator is bad. How much does one cost?
 
Re: Testing charging circuit on 75

not sure on cost, but the rectifier is probably bad as you said. First check the ac voltage from the stator to the rectifier.
 
Re: Testing charging circuit on 75

Tested the rectifier and stator both checked good. However when motor is running the voltage is all over the place. From 13+ to 4+ is the readings I get from battery. AC voltage good.
 
Re: Testing charging circuit on 75

Sounds like you have a short somewhere. If you have your manual, it will show continuity specs for the stator. Check that and all the wires from the rectifier.
 
Re: Testing charging circuit on 75

Did all the tests for rectifier and stator. Both check out fine. No loose or corroded connections. Voltage at the battery, solenoid and rectifier is within +/- .05 of a volt. Can the rectifier be messed up when under a load from the stator?
 
Re: Testing charging circuit on 75

Hey tritonman, think I have it narrowed to the rectifier. Even tho it tests fine I bet under a load it can't handle the load. All other wiring is ok. I checked ohms and continuity on all systems and it seems to lead back to a faulty rectifier. Will post results after replacement. Thanks.
 
Re: Testing charging circuit on 75

hey tritonman, Changed the rectifier and now all the voltages are staying on the positive side but still fluctuating. No shorts located anywhere on any of the wires from stator to the rectifier or from the battery thru the solenoid and to the rectifier.
 
Re: Testing charging circuit on 75

Tritonman, After rectifier replacement and a run on the lake the battery is getting some charging. When I first put the rectifier on, the voltage varied from 2 to 14+ and now the fluctuations are getting smaller. I guess that's better than what it was right. Maybe they will stop after a while? Thanks
 
Re: Testing charging circuit on 75

The starting battery is not over 13 volts. It won't hold over 12.65. Is that too low? Plan on changing it soon as I can afford it.
 
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