Merc charging system

Key west Tom

Seaman Apprentice
Joined
Jun 5, 2005
Messages
32
I have a 1997 V6 135 Merc that the system voltage will bounce up and down from about 17 volts down to 13 or 14 then back to 17 volts. This does this mostly after 10 min of high speed running. I bought a factory service manual at the time I bought the boat/motor and have followed the tests for the voltage regulators. The problem is that in the book, it says (at one point) to connect the ohm meter to the "thick red lead" the problem is that both of my regulators have two of the same size red leads. In the wiring diagram it shows all 4 red wires (2 from each reg) going to the same place, the battery side of the starter relay. On the front of the book, it says for models 1992 and up-mine is a 1997 model is there a newer book? what red regulator wire do I test (both of mine are the same size)? <br />I read in other posts that some have seen burnt areas on the regulator or damaged yellow wires, I have none of this. <br /> Also, in my FACTORY service manual, it lists only two charging system possable failures, they are under charging and consistly overcharging, my overcharging is momentary only. Also my tach works fine (no jumping around) <br /> I went ahead and tested the regulators like the manual said (testing bouh red wires) and both units failed the tests even the test of the tach circuit. I can't belive both regulators are bad.<br /><br />Any ideas?<br />Thanks<br />Tom
 

andy6374

Lieutenant Commander
Joined
Aug 4, 2005
Messages
1,617
Re: Merc charging system

Check your battery. A bad battery can give you readings above the 14V output that your rectifier should supplying. I had the same problem, but in the end it was the battery at fault.
 

Coolmaker

Petty Officer 2nd Class
Joined
Mar 15, 2005
Messages
134
Re: Merc charging system

Make sure that your termnals ie: ground and all terminals to battery, battery switch (if used) and at the starter solenoid are clean and tight. This is the usually the problem in these cases.
 
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