Thruhull transducer problem

walleye

I have a thruhull transducer on my '08 320 connected to my Garmin 5208. The depth readings were great until recently. Now I get a "5.5 feet" flashing reading most of the time, with the exception of when the boat isn't moving. When I stop, after a while it will sometimes begin reading accurately again until I get under power, when the flashing 5.5 ft reading comes back. The connection to the transducer appears to be solid via inspection in the engine room. Any suggestions on how to trouble shoot this? Thanks 

MarkB

The transducers don't last forever. They have approximately a 5 year life and then start losing strength. My guess is you need to replace the transducer.