GPS Repair Problems? Ask a GPS Technician for Answers ASAP
Your Garmin EcoMAP 74sv receives the depth signal from the transducer.
If the transducer is faulty or not connected properly, you will not get a depth reading.
If you were previously getting depth readings ok but they suddenly stopped, then check the connection from the transducer to the EcoMAP - remove the connector and firmly attach it again.
If that doesn't help, then you will need to try fitting a replacement transducer.