1967 Evinrude 100 hp tachometer

[starflite]

Hi: I have an original OMC tachometer made for the 1967-68 E/J 100 hp engines with capacitor discharge ignition. It is presently inoperative. I have sent the tachometer to a rebuilding firm in South Carolina . They asked me if the pulse voltage was positive or negative. All I know is that the pulse wire is hooked in with the wire coming from the pulse pack to the positive side of the coil and the voltage is approx. 250 v . Being that it is hooked up to the positive side of the coil would it be safe to say that the pulse voltage would be positive?
Any help would be appreciated. Peter

 

[racerone]

I thought those ran off the alternator pulses ?

 

[starflite]

the original tach ran off the pulse from the pulse pack. It wasn't till later in 68 that they had an alternator pulse tach.

 

[Boobie]

Correct........

 

[fdrgator]

That would be only an assumption. Having said that, I do not know if it is positive or negative. Your assumption has a 50% chance of being correct.

 

[starflite]

all is well. The original tachometer will only work with the original CD65 pulse pack which is positive pulse. The phase 2 pack which replaced the CD65 pack is negative pulse and will not work the original tach.