
Originally Posted by
vic n
It is possible that the speed has been turned off. You may have to go through this process for several "Readout Positions" and follow the instructions here:
Press the UP or DOWN Cursor keys to select a Readout position, then
press the RIGHT or LEFT Cursor keys to choose what will be displayed in
that position. To hide the data window, select Off. (Course, Navigation,
Off, Position, Speed, Temperature, Time+Date, Triplog, Voltage)
This is copied out of the 587/597 owner's manual at humminbird.com