1990 Evinrude 115 hp tach questions.

[oldsalt92]

I am the proud owner of new (to me) 1988 Bayliner 19ft Center Console Trophy. It originally came with a Force motor which has at some point been replaced by 1990 Evinrude 115 hp. Motor is in good shape but the tach does not work. I pulled the tach and it has a - purple wire to ign post-black wire to ground-gray wire to sense post-blue wire to light and a black wire to EI (or EJ) post. Wire colors are uncertain due to butcher job performed by previous owner. I have 12 volts at the ign post when the key is on. I do not know what the EI / EJ post is but what voltage should I have at the "sense" and EI/EJ posts with engine running?

I currently trying to resurrect a 1965 60 hp Evinrude and 1957 35 hp Johnson that I recently acquired for free, so I will be picking the brains of you all frequently.

Thanks for any ideas on this tach problem.