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wishing for walleyes

RPM gauge not working

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My rpm gauge has never worked since i bought my pontoon.I recently had the stator,trigger,and switchbox all replaced.Motor is a 1990 40 hp mecury.The light on the rpm gauge works but that is it.I traced the wires which run to the shifter box and they all appear to be good.I would assume the gauge gets its signal from the stator.I have a nice volt meter i can test it with,but havent a clue what voltage i should get.A bad gauge? Any thoughts? Thanks

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Check to see if your starting battery is charging.

Measure the battery voltage before the motor is running, then measure the voltage when the motor is running above 1/2 throttle. You should see a 2 volt increase or therabouts anyway. If you're not getting any rise in voltage when the stator went the rectifer probably went with it, which is why your tach might not be working.

If you are seeing a rise in voltage check under the hood for a gray wire where the harness plugs together - see if both wires from the control box side are connected to the motor.

marine_man

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Marine_man

You were dead on with the rectifier being bad.I went out last night and had no voltage increase even at wide open.Kinda makes me wonder about my mechanic.My stator was bad for sure,but he talked me into replacing the trigger and the switchbox all at once.Cost me $775 to have this done.I think my rectifier has been bad before the stator went because my rpm gauge has not worked for 2 years now.I would think he would have tested my rectifier.Thanks for your expert advise marine_man.

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