What is the adjustable switch attached to the Speedo on a 02

[jjgag60]

I have the 02 SANTE with the upgraded FARIA (sp) gauges and I noticed there are three wire attached to the back of the Speedo which runs to a chrome switch you can turn under the dash. The switch looks like a "gain" switch you would find on a stereo system. What does this switch do and what is the purpose of it. Thanks.

The boat is not running yet, so I don't know what happens when you turn the knob when the boat is running.

[TwinTip]

I believe you are looking at the knob that is used to calibrate the speedometer.

To adjust, you could go out to a course, if you have Perfect Pass with magnets, set the PP for 30 or 34 mph, run the course and check your timing, if correct, run it again and calibrate the speedometer.

Another option would be if you have a GPS. Accelerate to a given speed, keep it constant, then check the speed with the GPS and adjust the speedo to that speed.