tachometer not working with 25 hp Mercury outboard

[szn9rg]

I recently purchased a SunTracker pontoon with a 25 HP Mercury outboard. The tachometer doesn't work. How do I find out if the tach is bad or something else. I seen other forums which says there should be a rectifier and a voltage regulator. I know where the rectifier is but don't see a voltage regulator. The serial of the motor is OG376600 and is a 1996 25 EL. Can I test the tach at the back of it for a siginal from the motor and if so which wires do I connect to multimeter. Any help would be appreciated.:'(

 

[szn9rg]

Re: tachometer not working with 25 hp Mercury outboard

Is there anyone who can offer any advice for my tach problem. I need some feedback prior to Fridy evening. Thanks in advance for your time and knowledge

 

[ricksrster]

Re: tachometer not working with 25 hp Mercury outboard

There should be two yellow ( or yellow with a red stripe ) wires hooked to the regualtor. There should be a grey wire connected on the same rectfier post as either yellow ( yellow/red ) wire. This grey wire goes up through the harness to the control. You may have a little harness coming out of your control with a plug on it. This is for your tach. If you don't have the little harness or plug you can run a wire from either yellow wire connection on the rectifier and connect it to the send post on the tach. A wire from the ignition switch connects to the IGN post on the tach. This supplies 12v+ when the key is in the on posotion. Connect a ground to the ground post on the tach. The tach may have a light post. Connect a wire from your lights there. Set the little selector switch on the tach to 4P. That is all there is to hooking up the tach. Make sure your connects are tight.

 

[Barnacle_Bill]

Re: tachometer not working with 25 hp Mercury outboard

If it is wired correctly, check your rectifier. The easiest way is to check the voltage at the battery with the motor off and then check it again with it running. You may have to increase RPMs a little to see any change. A bad diode in the rectifier can keep you tach from working.

 

[szn9rg]

Re: tachometer not working with 25 hp Mercury outboard

Thanks for the help with the tach. It turned out to be a bad rectifier. After I replaced it, the tach worked fine. The only thing I'm not sure of is the correct setting for the tach. It was set on the 6P position but several others have said it should be on the 4P position while others say the 6P slot. Which is correct?

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