Hooking up a Tach

[dmwelch]

Hey guys I have a 1968 RKL 30 Johnson Electramatic 40hp and I'm trying to figure out how to set up a tach, I have a grey wore that runs to the front dash, but it's not connected to any think in the engine compartment? Where should it be connected to make it functional?

Thanks

 

[F_R]

That motor requires a magneto tach. Is that what you have? They are very hard to find nowadays. It gets its signal from a wire leading to one of the two sets of breaker points ("M" terminal on ignition switch). If I remember correctly, the grey wire is a tach ground to complete the hookup.

Modern motors get their tach signal from the alternator and won't work on your 40.

 

[boobie]

You could google Mini Tach and you may find something there that will work.

 

[gm280]

A Tiny Tach gets its input via a high voltage spark plug wire. It actually wraps around the high voltage lead and works very well. An older tach got their input via the points on the lower voltage side and that is how they worked. Both use a spark per RPM type conversion to read RPMs. The newer OB engines get pulses via the stator winding for their tach connections and that gray wire goes to one of the stator output connections at the input side of the rectifier. Just some info.