tach question

[mikesjohnson]

i have a '79 70hp 3cyl on the back of a 17'8" for the time being (i still need to get the 115 running). the motor came off my rotted 15ft tri hull. I know its not turning enough rpm, but i have no idea of where it's even at rpm wise. i was going to hook up a spare autometer tach that i have (a five inch "Monster" super duper racing tach; ohhhhhh!), but before i go through all the trouble of mounting the tach and running the wires, will it even work? i was figuring on wiring it up to one of the coils and swithcing it to a 6cyl setting. being that its a 3cyl 2 stroke, the ign pulses should happen at the same frequency as a 6 cyl 4 stroke, right? any help is greatly appreciated.

p.s. i know it's not a marine tach, but its only a temporary setup to determine the correct prop for the boat till the 115 is going again.

 

[JUSTINTIME]

Re: tach question

will not work
u need a 2 cycle tach
tiny tach they sell around $30

 

[GlasV162]

Re: tach question

If your control box has a 3-prong plug just below the ignition key switch, wiring a tach will be easy. Just get the wiring harness from an OMC dealer (if I remember, it's around $30.00), plug it into the control box, and attach the other ends of the wires to your new tach.