Tach needle jumping

[bobs715]

Only recently and occasionally the tach needle will jump up to a higher rpm and return to operating rpm. The jump is very quick and does not occur all the time. 03 Merc 50 hp makes no sound of it's rpms rising. Any idea what is causing this?

 

[bassman284]

Re: Tach needle jumping

First thing would be to check the wires on the back of the tach. Even if everything looks fine, go ahead and wiggle them loose and tighten them back up. If that doesn't work, you've gone beyond my tach knowledge.

My tach never did the jump thing, but about 3 years ago it would intermittently not work at all (02 Merc 60). Occasionally when it wasn't working I would thump on the dash and it would start working again but not always.

This year, it pretty much quit working altogether. I finally got ambitious and pulled off the dash to check the wires. Everything looked clean, no corrosion, and all were tight. I worked them all back and forth a little bit, loosening them up, then snugged them back down. Tach has worked fine ever since.

 

[fucawi]

Re: Tach needle jumping

bad connection ....if neccessary run a new wire all the way from the engine to the tacho