RPMS gone crazy

[yamimel]

hi, I was hoping someone on the forum has an answer to what is going on.
this is the problem, I have a 2004 yamaha 115. It has been running fine and the tach has been working great. For some reason the tach is not reading correctly now. it is reading way high and is eratic.. what used to be 4800 rpm is now 6-7000. I dont even know where to start . how can one minute it work great then the next its all messed up? Any feedback would be appreciated.

[99yam40]

what tach do you have?
If it is one with the switch in the back to set the pulses then it may be a bad connection in the switch. Turn it back and forth a few times to see if that will settle it down