SI Sensitivity: 8 to 12 (Lower for hard bottoms, higher for soft bottoms)
SI Enhance Settings: Off for Crisp Images - Low or Med to make it easier to see fish
---Sensitivity: This is the same sensitivity as above
---Contrast: I leave it at 10 most of the time
Scroll Speed: Make boat speed or a little slower 2-3 when idling for me
SI Transducer Frequency: 455kHz for largest coverage area (90% of time) 800 kHz when looking for more detail (10% of the time)
DI Sensitivity: 10-12 this is seperate of SI or 2D Sensitivity
DI Coverage: Wide for more data or Narrow when only looking under boat
Down Imaging uses the SI Frequencies 455 or with HDSi Transducer on 898c, 997c, 998c or 1197c, 1198c offers 800 kHz. I use the 455 kHz.
2D Sonar Frequency:
Switchfire Mode: Max for Vertical Fishing and Water over 10', Clear Mode when I want to see fish only
Sensitivity: Varies per conditions and which Mode I'm using
Transducer Type: 200/83kHz combined is best for most coverage area.
http://www.bbcboards.net/humminbird-sonar-gps/
There's a ton of info in this link. Those are Doug V's general settings. I actually copied and pasted those basic settings then emailed to myself, opening it on my phone and saving it to have on the water.