My depth sounder has gradually lost sensitivity over the years. Used to read over 800 feet in clear water, not lucky to see bottom over 200. I read once the control head can drift out of calibration. Is this true? If so, can it be recalibrated to improve sensitivity again?
That isn't correct. The depth transducer is made up of elements that output and receive the sonar signal. If you are noticing decreased performance, this is due to the elements inside the transducer are degrading or you are losing elements. The recommended course of action is replacing the transducer. Current instrument
Depth Transducers are compatible with the ST50+ Depth displays. You will need to cut the transducer connector off the ST50+ display, then remove the spade connectors off the current depth transducers and splice color for color to connect.