Tach is erratic

[chris in houston]

2000 Merc 60 HP 2 cycle on a 2000 bass tracker. Dash Tach became erratic last time out, bouncing around and generally showing RPM's that were not correct. Is this a bad connection under dash most likely? Thought I'd ask before spending time tinkering with it.

 

[Barnacle_Bill]

Re: Tach is erratic

Could be a loose connection or your rectifier could be going. Also look on back of the tach and make sure the pointer is pointing exactly to 6P. Close doesn't count. Work it back and forth a few times when you set it.

 

[j_martin]

Re: Tach is erratic

Could be a loose connection or your rectifier could be going. Also look on back of the tach and make sure the pointer is pointing exactly to 6P. Close doesn't count. Work it back and forth a few times when you set it.

Most tachs have a screwdriver switch on the back to set up the number of alternator poles it's counting. The switch gets dirty. Moving it back and forth, then setting it back where it was usually fixes it.

Otherwise, a bad rectifier, or grounding on the rectifier can make them quit or get erratic.

hope it helps
john