Tach bouncing

[ChilliSpoons]

The tach for my 75hp Merc is bouncing around and reading incorrectly. When I mash the throttle to get up on plane the tach jumps up to 7500 which I know is incorrect. It will settle back down to the correct rpm but will still jump around. The Merc is on a 2011 Lowe.

Where do I begin to solve this problem? Sending unit or tach?

 

[ship happens]

Has it always done that or did it just start

 

[ChilliSpoons]

Just started on first trip out this year

 

[Rain City]

Just started on first trip out this year

My Bayliner tach did that intermittently. I used to give it the ol' fist bump and it would stop. I believe it was just a bad ground in the gauge cluster that was the issue.

 

[ship happens]

Yeah then it's just a bad tach. El replaceo