Mercury tachometer application

[Dean rawson]

I have a 1980 115hp 4 cylinder 2 stroke, I am trying to find a tach , I picked up a merc 59081a1 tach which has several settings but none seem to be accurate, apparently this engine runs on 2cyl up to 2k rpm then on 4cyl, seems to me this would result in erratic pulses to tach, certainly mercury made a tach for this engine, I am looking for some direction on this dilemma
Dean

 

[Droid]

I don't believe you have a 1980 4 cylinder engine. Did you fat finger the year? 1988 or 1989 seems more correct. If it's a late 80s motor there is no idle circuit metering fuel to the 2 inop cylinders. Spark still happens.

Regardless, the tach reads off the stator, counting pulses of A/C output. IT DOES NOT SENSE SPARK OFF THE COIL LIKE A CAR. The selector on the tach is set to stator design, not cylinders.

 

[Dean rawson]

Droid, thanks for the reply, you are correct , it is a later year however I do not have fat fingers , s/n is oc238720 , that being said , the wiring diagram in the ( seloc) manual I use as a reference identifies the engine as one with a small regulator/rectifier , what setting do I use ,I am connected to the grey wire
Dean

 

[Droid]

I'm not sure but most frequently stators are 6 pole.

 

[Dean rawson]

Thank you, I will try that setting at idle with an old school tach and go from there