Hooking up two tachs to coil

[midnightrider1818]

Wanting to test how accurate my original in dash tach is. I was thinking about buying one from autozone and hooking it up too. Will two tachs hooked off coil negative screw accuracy up or cause a problem. Running thunderbolt iv. 89. Also what is the color of the original tach wire for this system. Thanks fellas. Also trying to prop boat so I'm trying to get accurate rpm readings

 

[Bondo]

Ayuh,..... I use the tach in my timin' light,.....

A cheap tach from the auto parts store may not be any better than the one in the dash,.....

That's why it recommended to use a known good shop tach,....

 

[Scott Danforth]

I use a hand-held laser tach on the crank pulley.

 

[achris]

20 tachos hooked up wouldn't be a problem. But yes, to you should be using a properly accurate tacho.

Grey.

Chris...