Hi:
I can try to help but I would need more detailed information. Like where are you mounting it on your boat. On the transom below the water line or on the trolling motor or though the hull. That can make a big difference.
I may be going for a new humminbird depth finder someday and then I will have to install a new trasducer on my boat. I want one for the transom on the back of my boat for high speed operations so I don't run into a shallow water stump bed accidently and then I want another transducer that will attached to my Minn-Kota Trolling more.
Let me know what type of transducer you have. Some unit (Humminbird Matrix 47D will go into simulation mode automatically if the transducer is not attached or defective.