Tachometer goes backwards

[pensacola]

I have 1999 mercruiser 305 5.0. It first started out by going up to like 5000 rpms at idle. The motor was idling at normal rpms but the tach said 5000. Now it stays at zero when idling. When I rev it up it goes backwards below zero all the way over to 5 or 6 thousand rpms. Is this just a bad tach or what?

 

[180shabah]

Re: Tachometer goes backwards

If you have had no recent wiring changes, I would definately be looking at a new tach.

 

[Chris1956]

Re: Tachometer goes backwards

Check your connections. Make sure the +12V is on the ign terminal, -12V is on the gnd terminal and the dissy is connected to the snd terminal. Especially check to make sure it is getting a good ground.

if all this is good, the tach may be bad.

 

[pensacola]

Re: Tachometer goes backwards

The connections are good. Its acting right sometimes then it goes backwards sometimes. Its gotta be the tach in my opinion.