gauges jumping

[MJS]

My tach and gas gauge jump sometimes but not all the time. Sometimes the tach jumps to 65k when there is no change in rpm. A quick tap in the glass brings it back down to where it should be. Sometimes they just bounce all over the place. Whats up with that? Also sthe speedometer doesnt start to register until you hit about 20mph.

 

[pnwboat]

Re: gauges jumping

You may need some new gauges. My tach did the same thing. Always had to tap it to make sure it was giving me the correct reading. Replaced it and solved that problem.

The speedometer has a small plastic tube that goes from the back of the gauge all the way back to the transom to a hard plastic pick up. The plastic pick up is normally spring loaded so that if you hit something like a small branch, it will kick up thus avoiding breaking off. Make sure it's all the way down, and that the tube that runs between the gauge and pick up is not plugged.

 

[jerryjerry05]

Re: gauges jumping

What we working on??
The older tachs(mine do) jump or die, then a lite tap and it's ok.
Like PNW says replace.

Speedo pick up.Could be the pick up in the lower unit or the pitot tube on the transom.
Or a slight pinch in the hose.Follow the wiring harness and see if it's pinched.J

 

[Jlawsen]

Re: gauges jumping

Bad negative connection.

 

[MJS]

Re: gauges jumping

What we working on??

1990 bayliner trophy CC 120hp