tach prob

[river_ratj40]

just got a teleflex tach. hooked it up to 56 cu johnson. when you start the motor all looks good. at wide open throttle the tach pegs out, then about a min into wide open throttle the needle returns to normal rpm. but every once in while it will peg out and then return. whats up with my tach???

[sst45jefff]

probably the wrong pulse setting or the wrong tach for the year motor you have.

[Brian Burkhardt]

If it has it, set the pulse setting on 6 and then try it.

Brian

[Haych]

Hi River Rat!

Had the same problem a while back.

Are you running the tacho off of a battery or direct from a rectifier on the engine.
If straight from the rectifier, you won't be getting a constant 12 volts. It jumps around a bit from 12 v at idle to 14 + v at revs. Thats why the tach needle pegs out then dies etc etc until revs return to 12v or very close to.

Hooking a battery up allows constant 12v supply to tacho. Connect the rectifier to the battery to provide charge while engine running.
Tacho setting is important to. Instructions or manufacturers website could help there.
Otherwise you can get a 'tiny tach'. Only need to wrap red wire around plug lead and white wire to ground/earth on the engine block. Gives digital readout. Small, nifty unit. Own power supply. Not much bigger than a box of matches.

Hope it helps :cool: