Tachometer hookup

ferdly1

Petty Officer 2nd Class
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Jul 30, 2012
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194
I took the boat out for first time with the 1997 Force on it. It really performed well. I want to thank everyone here for their help. It has been a long slow process. I call this my motor from hell.. Still have some minor problems to fix. My tachometer is not working, although it may be the gauge. Seems I was having trouble with it last time I took it out. I had an 1988 90hp evinrude before. I measured the gauge and it is 4 inches across the face. So I guess I need a 4 inch gauge. Just wondering if there is anything else I should check if that doesnt fix the problem. The motor is charging the battery. I just thought of something. What wire from the !997 75 hp Force goes to the rpm gauge.
 

Frosty1308

Cadet
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Mar 20, 2017
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11
I've been looking into adding a tach to my 95 Force 120. From what I've discovered it's the grey wire coming from the wiring loom that gives the tach output. If you've got a multimeter you should see some sort of AC voltage on that wire (ground anywhere reasonable) if all is working OK. Can't really tell much about RPM from the AC voltage alone but it does show the wire is working!
 

jerryjerry05

Supreme Mariner
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May 7, 2008
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17,923
The size of the tach is measured from the back.
​It's a standard size hole.
​99% are 3 1/2" or something like that??
​Being as it a 97 the electronics are Mercury.
​All Mercury's use the same color code.
​I believe Grey is the tach lead(I think) older Force is Purple(I think).
 

ferdly1

Petty Officer 2nd Class
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Jul 30, 2012
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194
Thanks for replying Jerry. We are talking about the leads that come from the alternator aren't we. Heres a crazy one for you. I looked at the motor and there is a purple and grey wire coming from the alternator. Crazy thing is the gray wire is hooked to purple wire going to the coil. The puple wire isnt plugged in but has a plug on the end. Just wondering if the grey and purple wires arent reversed or does it really matter. Motor runs fine. Going to order a tach anyway But when I order choices are 3" or 4". Also wondering when i order the gauge if the rpm on gauge matters. Mine has 8k on it although the evinrude and mercury should never go over 6k.
 

Frosty1308

Cadet
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Mar 20, 2017
Messages
11
If yours is a 97 you should have roughly the same electrics as me (95 120HP). From what I've discovered so far I can say with some certainty that the purple wire is the ignition live (i.e. 12V when key is in ON position). You may find that that disconnected plug is a branch of that purple wire. It also looks like the grey is the tach wire (though I haven't had chance to verify this yet). You should find it coming from the regulator on the starboard side of the engine, threading under/behind the flywheel and down and out through the main harness.

I know the below is for a 120HP, but they both have very similar electrical/ignition systems, so hopefully it should be of some help.

http://www.maxrules.com/graphics/force/wiring/120HP_96_up.jpg
 

jerryjerry05

Supreme Mariner
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May 7, 2008
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17,923
The tachs that measure up to 8K are for the racers among us.
Some of those guys regularly run up to 7-8 K
 

ferdly1

Petty Officer 2nd Class
Joined
Jul 30, 2012
Messages
194
Thanks guys. So I guess its ok to use a 6,7 or 8k tach then? Also I see the Gray wire that goes to the switch. Where is the wire that goes to the tachometer from the switch. On this particular. remote control there is a pigtail coming out of the remote control. Looks like there is a gray wire as part of this plug.. Cant imagine I will find the other plug that hooks to the pigtail. I guess I could cut the gray wire from the pigtail and run to tachometer. Oh and thanks for the diagram!!!
 
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ferdly1

Petty Officer 2nd Class
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Jul 30, 2012
Messages
194
According to parts breakdown here is a picture of the tachometer and accessories hookup cable.
 

jerryjerry05

Supreme Mariner
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May 7, 2008
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17,923
You'd have to find a parts diagram that includes the shifter and wiring harness.
The wiring is something that is more to the boat and instruments than the motor.
A Mercury dealer would be the best bet.
 

ferdly1

Petty Officer 2nd Class
Joined
Jul 30, 2012
Messages
194
I found a diagram of the shifter and harness but it doesn't show the cable that plugs in. Probably will cut the wire there and run it to the tachometer. Mercury dealer closed down here.
 
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