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Adding New Tachometer

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2ifbyc

New member
I have a 95 Force by Mercury 70hp outboard on a 17 foot sea pro (wasn't sure if I should post here or mercury thread). The boat currently has no gauges other than a fuel gauge. I would like to add a new aftermarket tachometer. I know how to connect it but I am having trouble locating and identifying the correct signal wire from the engine. Anyone know how I can determine which wire and where exactly to find it at the helm? Most of what I've read seems to be either a grey or a purple wire. Also, should the wire be there just waiting to be connected or will I have to cut an existing wire from somewhere? Any help is appreciated. Thanks guys
 
Usually the harness from the motor to the shifter or dash will have a wire in the harness.
Usually it's taped back.

They used Mercury and Force shifters and wire harness's.

Post a pic of the shifter and the wire harness on the stbd. side of the motor.
Is it the 8 pin connector? That's Mercury equipment.
You'll need to use a photo sharing site, this site requires 5 posts before it allows you to add pics on here.
 
Jerryjerry05 said:
Usually the harness from the motor to the shifter or dash will have a wire in the harness.
Usually it's taped back.

They used Mercury and Force shifters and wire harness's.

Post a pic of the shifter and the wire harness on the stbd. side of the motor.
Is it the 8 pin connector? That's Mercury equipment.
You'll need to use a photo sharing site, this site requires 5 posts before it allows you to add pics on here.
Click to expand...


I traced the grey wire from the rectifier to the dash, connected the gauge and it went 0 when I turned key but never moved off zero with engine running. I believe I either have a bad rectifier or a bad gauge. Pretty sure its the rectifier because the gauge was working fine on boat it came from. The guy I boat the boat from said he just replaced the rectifier but he thinks he attached the battery leads backwards one day and possibly saw some smoke coming from the rectifier. I think Im going to start with replacing the rectifier and see where that gets me. As of now theres no signal getting to the Tach or the Tach is bad. Well see I guess...
 

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From the pics it's Mercury ignition.
Yup smoke's a pretty good indicator of a problem. :)

Bad tach: usually they don't go bad unless it's fed a lot of voltage.
Try hooking the wires backwards and see if that makes a difference?
 
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