1978 mercury 115hp

[buzzm19]

I need some help from the experts, I have an over charge problem 16volts. When everything is connected the tac is eratic, when I disconnect the red wire on the rectifer everything returns to normal tac settles down. I am not sure where the voltage regulator is, In the switch box? All wiring is good bat is super heavy duty, I realize when I disconnect the red wire on the rectifer that I am only running off the battery. Is it possible the stator is spiking and causing an over charge or if so the voltage regulator is bad. Thanks Buz

 

[Barnacle_Bill]

Re: 1978 mercury 115hp

You don't have a regulator on that motor. Common causes of high voltage is non marine battery being used, bad or dirty connections or a bad battery. Or you could add one of these http://www.mfgsupply.com/m/c/01-090-1.html

 

[buzzm19]

Re: 1978 mercury 115hp

Thanks for your reply, all the connections are good and clean the battery is marine super duty from sears with 1100 cranking amps, the best. Is it possible that the stator could be spiking eradically to cause this. thanks Buz

 

[chum1]

Re: 1978 mercury 115hp

I doubt you have a voltage regulator, probably just have a rectifier, if you can make a base plate out of sheetmetal you can install one of these, works great on my 77' 850 and wont catch on fire

http://www.allelectronics.com/make-a-store/item/FWB-352/35-A-200-PIV-BRIDGE-RECTIFIER//1.html

 

[Chris1956]

Re: 1978 mercury 115hp

Buzz, When you disconnected the red wire at the rectifier, you very likely damaged the rectifier. You now are charging the battery with AC voltage, which is also reaching the tach, possibly causing damage or at least erratic performance.

I recommend you replace the rectifier.

BTW - The starting battery functions as a voltage regulator on that system. it serves as a load to hold the voltage down. Give it a chance to do it's job and you will see that it works just fine.