Need to select tachometer for Force-85

To advance my hunt for the correct propeller i think i need to get a tachometer and see what my current prop does as far as speed and RPM go.

So my question is this,

are all marine tachometers the same?
if not, what am i looking for in a tachometer to make sure it will give a proper reading with the force-85?

i believe my force is the 1987-1989 model from what i can tell from looking at wiring diagrams in the book, which is strange because the boat is an 83. I can't find a 1983 85hp diagram. Also, the 1984-1986 wiring diagram looks nothing like mine, it doesn't have a neutral switch, choke solenoid, or temp sensor but i guess i could be wrong - the diagram may just be incomplete.

anyway,
Thanks
-Mark

Re: Need to select tachometer for Force-85

Yours is different from most outboards. You need a tach made for a 20 pole alternator like Teleflex's 53743P.