Lowrance HDS Gen 1 and 2 Keypad Models 5, 7, 8, and 10 Sonar Settings On October 30, 2013
Doctor Sonar Freshwater Settings as a starting point
The most common freshwater transducer is the 83/200 kHz, when you select this you will not have the choice for 50 kHz as a menu selection since it doesn't work with the 83/200 transducer. Generic works the same as selecting the exact transducer for sonar images.
Gen 1 doesn't have Auto Contrast and the latest software for Gen 2 has Auto contrast which works well.
Contrast has no set preference. It needs to be adjusted differently for depth, palette and your preference; 50-70 usually works and always adjust higher as you go deeper.