I have an older Johnson motor that I need help with. I would like to install a tachometer on it but I am not sure how to do this. I can not find the wires to wire it up from the motor.

Where do you find the wires ??? Where do they come from on the motor? The plugs? I don't have a clue and I don't see any additional wires coming from the motor.

It is a 140 HP Johnson (1979). Someone before me cut the wires to the tach and now it isn't working.

shouldn't these connect to the pickup under the flywheel somehow? i'll look in my manual tonight and see if i spot anything.

There should be a connection in the throttle/shift controls.

Thanks Bigbob_FTW. If you can find something out, that would be great.

It could be in the shift controls as well though, not sure. It makes sense though, seeing how you would have to rewire it back into the boat, unless they cut the wire from the motor.

If your control box is side mounted and is a 1979 model there is a pre wired plug under the ignition switch that you can plug a tach wiring harness into and run straight to the tach. I believe we can still get the harness. Let me know if we can help you.

Tommy Yetts
Rockwall Marine

Going out to look under the control right now and check it out. I will let you know what I find out. Thanks everyone. God this forum is great.

I looked under the control box and it has one cable there it extends out 3 to 4 foot and it cut. There is a black and red wire on it. I assume that is it and they (previous owner) cut it. So that runs straight to the tach then? Which one goes where on the tach?

I think the cable may be corroded or even split right before it goes into the control box. I wish I had a digital camera to take a picture of it, that would be alot easier.

I don't see where the grey cable on the tach go. The harness under my control box will be ground and power, but if the grey wire goes to the motor, where in the world does it go?

I think the grey wire goes to the volt regulator--

And that would be where?

Two black knobs under the keyswitch on your control box - the First is the throttle tension knob, the second is the plug for the tach covered by a rubber boot. Pull the boot off, you'll see a 3-hole socket. the harness Tommy mentioned plugs into that. The three holes are connected to purple, black, and gray inside the control box - purple is 12-volts switched, black is ground and gray is the tach sender.

set your tachometer selector to 6P.
Connect the IGN post to the purple wire (post A on the ignition switch)
Connect the LT post to your panel light switch or your anchor. light if you don't have a separate panel light.
Connect the SEND post to the gray sender wire.
Connect the GRD post to any good engine ground (black wire).

I will take a look at that tonight then JTEXAS. Very good description by the way, thanks.

I know I have the tension throttle knob on there, but don't recall a second plug on it. The throttle knob is actually not under my ignition switch where the key goes. It is on the opposite end. Is it underneath possibly where the red and black wire are coming from?

Could be - I'm not familiar with it though - if it is factory wiring, red means constant 12V. Otherwise it's do-it-yourself, maybe tapped into the box for accessory power. You could check the wires with a multimeter - if you get AC (or maybe it's pulsed DC?) with the engine running, then it's the tach sender - otherwise you'll probably see 12V DC either constant or switched. In any case, I'd probably want to visually inspect the connections inside the box before hooking those wires to anything.

let us know what you find

I sure will, thanks for the info.