How to fix jack plate gauge kit: First, try to calibrate the gauge kit with a gauge magnet bracket. For your gauge kit to read properly, your sender assembly must be properly calibrated with the gauge magnet bracket.
To accomplish this, run the jack plate all the way up and loosen the two Phillips-head screws on the gauge magnet or “L” bracket enough to manipulate the angle of the bracket.
By sliding the bracket up and down or side to side you can align the magnet so that the sender assembly can detect it.
Once you have it aligned, lower the bracket so that it is just above 19 and still reads 20.
Tighten the bracket again and lower it all the way to check that it stops at 0.
If the unit still does not read 0, raise the sender assembly. To raise the sender assembly, loosen the Phillips-head screws on the sender assembly and raise it up a bit.
Then repeat the steps by tightening the screws on the sender assembly and loosening the screws on the gauge magnet bracket, lowering it so that it is just above 19 and still reads 20. When you have done this, lower the plate all the way.
Please note: In some cases, you will have to raise the sender assembly substantially.