1978 mercury 115hp

[buzzm19]

Here we go again, I have this motor and its been a problem that seems to me that its producing too much voltage (16-17 volts) when I throttle up. I have read a lot on this forum and most say to add a voltage regulator. To a point I can see that as a simple solution, the only thing is that mercury ran these motors from 1970-1978 without a regulator and was not a problem. I believe that it has only a 9amp stator and also ran the same motor in 1971 135hp in its stock form and never had a problem. Both motors have volt gauges so I can compare, I do remember the 1971 and we were careful not to run too many accessories because of the low charging system. So if these motors didn't need this before then why now? Thanks Buz

 

[Dave1027]

Re: 1978 mercury 115hp

The battery is the regulator on the low amperage systems. If it floats my boat that's good enough for me. I got bigger fish to worry about.

 

[Ben.Skelton]

Re: 1978 mercury 115hp

From my recent experience with a '79 90hp. When the voltage starts running high like that, you likely have a short in your stator. My rectifier was the first to blow out, replaced that, and then my stator went out. Good luck with your motor. Mine is put up for the winter until I can afford to repair it.

Ben

 

[bobkyle2]

Re: 1978 mercury 115hp

is your battery in good shape?? ive seen batterys loose a cell and it will overcharge... i dont know if that is your case but ive seen it done on vehicals

 

[Chris1956]

Re: 1978 mercury 115hp

Check to make sure the rectifier is good, and all wiring is clean and tight. The battery is sufficient to regulate that system. A VR is overkill.

 

[75TowerOfPower]

Re: 1978 mercury 115hp

Mine does the same thing. I replaced my rectifier 2 years ago with one from Radio Shack and when I am at WOT I motice the battery guage says 16 or so on it. I know battery is good and rectifier should be good. So I was thinking of adding a regulator as well. Anyone add one? I know Arch builder added one to his MissMorgan project and it's a digi one with a 12.4V max or something. Maybe he can chime in.