Setting a tach up

[v12mac]

I bought a tach for my brother and when I hooked it up all was well but the reading was off around 500rpm at idle. So I went to change the setting on the back of the tach and this thing is like a rheostat on the back. It is completely arbitrary to where you think it should be. Is this just a low quality gauge or is this the norm? I want to be very accurate in the reading as we are dialing in the prop on this boat now.<br />Mac

 

[Dunaruna]

Re: Setting a tach up

Is the gauge secondhand? it sounds like the markings on the adjuster may be worn off. Another possibility is that the adjustment is for 'fine' only. You'll need a reference tach (a shop tach) to check your adjustment.<br /><br />Aldo

 

[v12mac]

Re: Setting a tach up

It is new and has a sticker slapped on there with 1-9 numbered on the back. No notches in the "dial" it is very goofy. Is this the norm? Why wouldn't it just have a setting V8 4 stroke?<br /><br />Mac

 

[Dunaruna]

Re: Setting a tach up

What brand & model is it?

 

[v12mac]

Re: Setting a tach up

Not sure of brand some crap from overseas.<br />Where can I get a shop tach? I need to know with in 100rpm of where this motor is running.<br />Mac

 

[Dunaruna]

Re: Setting a tach up

A shop tach is one that connects to the neg coil terminal. A good multi-meter or even some timing lights have tachs built in.<br /><br />I can't help any further, it's possible that it is designed for one application only - 4, 6 or 8 - not all.<br /><br />Aldo