Tachometer accuracy

[Todd Humphreys]

I recently purchased a tach from Teleflex for my 1982 Johnson 75hp, and the last time I ran the boat the WOT was 6200 rpms and idle was 1200 very smooth "ideal"(900 in forward). When in gear at 900rpm the motor is on the verge of dying, but looking and listening to the motor it would seem to idling at about 650-750rpms. Do tach's need to be adjusted to each motor or are they good to go straight out of the box? Thanks

 

[bh357]

Re: Tachometer accuracy

There will be a switch on the back of the tach. Make sure it is set to 6P.

 

[gaugeguy]

Re: Tachometer accuracy

Hey DD, a marine tach right out of the box, set for the 6p setting should be accurate within +/-2% of actual. Teleflex may have a "fine tune adjust" potentiometer on the back that you can turn to dial in the exact RPM's on your tach.

 

[rodbolt]

Re: Tachometer accuracy

if your setup has a 4 wire rectifier you may need a tach with 5p some tachs show a j/e setting.<br />I always check new tach installations. some are way off out of the box.<br /> good luck and keep posting