Tohatsu M70C tach pegs when running. Need wiring diagram.

[Eddie V Gleaton Jr]

I need some help please. The analog tach on my M70C stays pegged all the way over when the engine is running. I have the Owners manual and Service manual but it's impossible to make out the wiring. Any drawings, suggestions or help of any kind will be greatly appreciated.

 

[Chris1956]

What is a M70C? Some kind of motor? Outboard, inboard or I/O?

Tachometers usually need +12VDC, ground (-12VDC) and a signal from the stator for an outboard or from the negative side of the distributor for an inboard or I/O. Simple wiring usually.

 

[GA_Boater]

Same question as Chris - What is an M70C?

Is this new problem and the tach just started pegging?

 

[Eddie V Gleaton Jr]

I'm sorry everyone, it's a Tahatsu 70hp outboard motor. I was attempting to post in the Tahatsu Outboard forum area. Please excuse a new user.

 

[GA_Boater]

Moving this the Tohatsu section.

 

[pvanv]

The white wire from the motor is the tach signal. You also want 12v and ground, and possibly 12v for the light. For the 70C, set the tach to 6 poles. If you have a non-alternator tach, you are stuck. Get a real tohatsu tach.

 

[Eddie V Gleaton Jr]

Thank you everyone. I'll do some testing with this info.

 

[Eddie V Gleaton Jr]

Hello again. I am using a Tohatsu tach. When I put a test light on the signal lead with the motor running it remains steady on, not flashing as someone stated it should. Any suggestions of where to check next would be greatly appreciated.

 

[pvanv]

A test light will not test what you want; you would need an oscilloscope. Does the tach peg with the ignition ON but the motor not running? If you you have an issue, possibly a bad tach meter or bad wiring.

 

[Eddie V Gleaton Jr]

Thanks for the reply Paul. The meter does not peg when the ignition on but the motor not running. I have also been told you can check the signal lead with an AC voltmeter. Is this also inaccurate? Thanks again

 

[pvanv]

Dunno. Never tried it.

 

[Eddie V Gleaton Jr]

Appears to have been the tach. Replaced existing with one I had on the shelf and appears to be working OK. Thanks everyone for your help.

 

[pvanv]

Was the old tach set to 6 poles?