Tom,
I replied to your PM about loading an older version software and than reloading the current version software. I don’t think it will help but you can certainly do it. You will need an older software upgrade (*.bin file) file to do this which I can send to you.

Where is your transducer mounted and what do you have the Transducer Select menu set to?
You should be seeing a lot more ‘stuff’ on the display or you are fishing in some of the clearest/cleanest water that I have seen. Is there anyway that you could test your 777c2 unit on someone else’s boat that runs a Humminbird? This does not have to be another 777c2 unit as most use the same 200/83kHz sonar (even most of the Si units). Just connect the power and transducer for the test (not the GPS).