Voltmetertach erratic advice please

[paul alagna]

" I have a 1987 Johnson 225 an

" I have a 1987 Johnson 225 and most of the time the tach seems to read correctly and the voltmeter displays roughly 12.5-13 volts when I am on plane. But every trip lately the tach will start swinging wildly or display a reading 1-2000 rpm's lower than what I am running at and the voltmeter will spike up to 17-18 volts. Sometimes just the voltmeter spikes and the tach stays normal. Seems to happen most often in rough water and or after the motor has been running for 20-30 minutes. I am worried that I am going to fry my electronics or worse. Could it be my regulator/rectifier or a bad ground or? Any ideas,suggestions would be greatly appreciated. Thanks. "

 

[joereeves]

"Paul.... Usually when you hav

"Paul.... Usually when you have both the tachometer and the voltage acting up at the same time, it is due to a failing Voltage Regulator/Rectifier assy. Of course it's always possible that a wire is loose, chafed, frayed and arcing to a ground somewhere.... but as I've said, it's usually the regulator assy. While you're checking that item, make it a point ot also check the magnets in the flywheel to make sure they haven't come loose, and also check out the large black coils on the stator assy under the flywheel. The heat of the 35amp charging system has a habit of causing them to crack and/or melt down.

Joe

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