Chesapeake White SS 4 Speedometer - 80MPH PitotPerimeter-lighted White dial with stylish Blue and White graphics, polished stainless steel bezel, contoured White pointer and domed glass lens.Electronic speedometers operate by capturing pulses produced by a sensor. the pulses are then electronically converted to a speed reading very much like a tachometer converts ignition pulses to RPM.Pitot tube type speedometers operate by pressure from the water being forced into the pitot tube. This pressure