Sadly, Garmin's manual is [censored]! Garmin gives only 4 pages of info in their manual explaining sonar and imaging.
For your console 73sv: Depending on your transducer, set to both 77/200 kHz. Set Max Depth to Auto.
For the Stryker 7sv: A lot depends on whether you are using a US2 transducer or the supplied Garmin transducer.
Garmins are difficult to set up and simply using the factory settings isn't enough. They require more active tuning on the water in both shallow and 30' deep water to find settings that read well in multiple settings.
Unfortunately unlike HB and Lowrance where I can provide good starting spots, Garmin must have all the settings gone through. Changing one effects others. If you have a friend that also has Garmin, get his help. If not, you will need a person on the boat that understands their system and settings. It takes about two hours +/- at several water depths to get the units tuned to provide accurate info. Garmin simply isn't user friendly.
If you have reached your point of frustration with trying on your own, contact me and we will talk.
Capt. Craig Copeland
Licensed by the US Coast Guard
2013 Nautic Star 2110 Shallow Bay Boat
Humminbird HELIX 12 CHIRP MEGA SI GPS G2N
Nautic Star Boats Pro Staff (nauticstarboats.com)
Redneck Fish'n Jigs Pro Staff (redneckfishn.com)