I had a friend of mine took his dad's boat out one night, went out on the water, turned on the fish finder, and fish were all over the screen. He and some friends fished a few hours without NOTHING! LOL Then he figured out that when he turned it on he had held the button down and the unit was in display or test mode, he turned it off and back on and there was nothing below him.
Back to your question. I turned the fish id off on mine, because it was lying to me and it has helped me a lot. I find fish and do have luck catching them sometimes, but I am mostly looking at the bottom contour and for baitfish.