Tach for Merc outboard

[Corvairdave]

I am wanting to install a tachometer on my Merc 20 jet. I have Quicksilver controls with a single brown wire connector and a 4 wire connector coming off the back of the controls. Do any of these carry the signal for the tach? TIA Cheers, Dave

 

[Chris1956]

It very likely does. The tachometer takes black, purple and grey wires. You will need the adaptor that brakes out the 4 wire plug. I bought one last year, but cannot remember it's part number. It took a bit of doing to get the P/N from Mercury, but I think amazon had the cable. Check on crowleymarine and the other motor parts and accessories site.

The brown is likely a temp gauge, as you have the overheat buzzer in the control, right?

 

[Yegboats]

 

[Corvairdave]

Thanks for the reply, Chris. I will check Crowley and see if I can find the number. I bought a Merc tach, but had no wires with it. However the tach part # might lead to a wiring harness #. Not sure about the overheat buzzer. Under the motor cover, there is a loose brown with a connector that has no home. I'll check to see if it's become unplugged

 

[Corvairdave]

View attachment 359875

Wicked! Thanks alot. Cheers, Dave

 

[Corvairdave]

Thanks for all the help! Working great with the Jet20. Put my Mariner 25 on and tach doesn't work. Also, seems like it's not charging as well. 12.5 volts running with brand new battery. Mariner is a '96, Jet is an '03. Hopin for something easy and obvious ;-) I'll start troubleshooting in a bit :-/

 

[Corvairdave]

I just wanted to clarify my earlier post. I bought a Mercury tach and the proper Mercury tach harness. After installation, I fired up my 2004 Merc Jet20 and the tach worked great. I took the jet motor off and put my 1996 25 Mariner on and now the tach doesn't work. Same harness on both motors. The motor swap was the only change. I'm wondering if there is something different on the 25 Mariner that doesn't send a signal to the tach. Any help would be great. Cheers, Dave

 

[Chris1956]

The signal for the tachometer originates in the rectifier or voltage regulator, whichever you have. Pull the cowling off the '96 motor and trace the grey wire. It should connect to something. It does have a charging system, right? Not all 25HP models do, especially non electric start ones. If no charging system, maybe no tach signal.

 

[Corvairdave]

The signal for the tachometer originates in the rectifier or voltage regulator, whichever you have. Pull the cowling off the '96 motor and trace the grey wire. It should connect to something. It does have a charging system, right? Not all 25HP models do, especially non electric start ones. If no charging system, maybe no tach signal.

Awesome info, thanks so much for the response. I will check that. If memory serves, I may have put a starter on this motor as there wasn't one.

 

[Corvairdave]

Awesome info, thanks so much for the response. I will check that. If memory serves, I may have put a starter on this motor as there wasn't one.

Good call. It's an 25ML model, so no charging system. It seems someone has made some changes though as there is a rectifier installed on it. Could a bad rectifier cause no tach signal? I have a new rectifier in my parts box and could try it.

 

[Chris1956]

Yes, a bad rectifier can cause loss of tach signal. Is the grey wire actually connected to the ac side of the rectifier? That is obviously necessary. Does your engine wiring harness even have a grey wire?

 

[Corvairdave]

Yes, a bad rectifier can cause loss of tach signal. Is the grey wire actually connected to the ac side of the rectifier? That is obviously necessary. Does your engine wiring harness even have a grey wire?

Yes, there is a grey wire, I will check to see which side of the rectifier it is attached to.

 

[Chris1956]

It looks to be wired correctly. Maybe the rectifier is bad. Disconnect the stator wires from the rectifier and connect the grey wire to one of the stator wires, and see if it works. If not the stator is either bad or incompatible with the tach.

Do not disconnect the battery wire from the rectifier, with the stator wires still connected and run the motor, That will blow the rectifier.

 

[Corvairdave]

It looks to be wired correctly. Maybe the rectifier is bad. Disconnect the stator wires from the rectifier and connect the grey wire to one of the stator wires, and see if it works. If not the stator is either bad or incompatible with the tach.

Do not disconnect the battery wire from the rectifier, with the stator wires still connected and run the motor, That will blow the rectifier.

Looks like the stator is bad. I'll pull the flywheel today and inspect. Thanks again!

 

[Corvairdave]

Pulled the flywheel. Everything looks ok.... Is there a definitive test for a stator? Like resistance across the leads or something like that. I've included a couple pics. Two magnet flywheel is the one that was installed, and 4 magnet one is a spare

 

[Chris1956]

There certainly are resistance specs for stator coils. I do not know what they are for your stator. As long as it is not open or shorted, it is probably good.

On some of those manual start motors, the stator is really a lighting coil. Expected to run some lights only.

I am not sure how that is different from a battery charging coil.

If you can find a part number on the stator, you should be able to determine what it is.

 

[Corvairdave]

Thanks Chris. I'm pretty sure this motor has been 'Frankensteined', so all bets are off. I'm sure the auxiliary stator and rectifier were added after. I wonder if when they modified it, they should have included the 4 magnet flywheel? More charging capacity? I might throw it on and try it. Thanks again.

 

[Corvairdave]

Twas the rectifier after all. Put the 4 magnet flywheel on, no change. New rectifier, tach works and looks like it's charging! Thanks for all the help. Cheers, Dave

 

[Chris1956]

Glad it worked out.