Weak Bottom Echo, Unstable Depth Reading, or No Fish Signals.
a) Make certain the transducer is installed properly.
b) Extremely heavy vegetation may confuse the sonar signal, causing it to misinterpret the depth. If you are certain that the readings are incorrect under these conditions, discontinue use.
c) Oil, dirt and fuel might cause a film to form on the transducer and reduce its effectiveness. Cleaning the face of the sensor might help.
d) Electrical noise from the boat's motor can interferes with the sonar, which will cause some weaker signals being eliminated.
e) Please check the battery voltage. The unit's transmitter power will decrease due to the voltage drop. And this will reduce its ability to find the bottom or targets.
f) The sonar might be in turbulent water. Mounting it in a smooth flow of water might help.