Lowrance X50ds fishfinder questions

Has anyone used ? or have a Lowrance X50. I have tried everything they suggest but still can't get fish to appear as an arch. If I adjust the sensitivity up to try and show that the screen goes crazy. It is currently used in a water bath and I have hung it over the side with little to no change. I'd rather not use the zoom in feature because sometimes the fish are anywhere from 5'-50'down. If I use the fish I.D. it lies, and shows a thermocline as fish. An upgrade is not an option at this time as much as I'd like to go to a color screen w/gps. Any advice would be greatly appreciated.

Thanks,Tim