tach question

[mercury400m]

hey guys i am buying a tachometer for my 1982 mercury 70hp 3 cylinder and i was wondering how many poles i have

im on ebay all the time and all i c is 4/6/8/12 pole tach's and am completly lost to which 1 is 4 my merc

[whaledog]

Stator driven tach is usually 12 pole some early V6 were 10 pole.

[john miffco]

most tachs are made for 4 stroke motors
which spark every 2nd revolution
so in turn a 2 stroke sparks every stroke

so most of the time
setting a tack for 2 stroke,,,,,,,, double the pulse
the 3 cyl motor the tach will be set at 6 pulses,,,,,,,,,,,,,
there is a few odd motor pulses,,,but the majoraty falls in the double the cyl catagory
john