Transducers will be filled with moisture over time, especially without the rubber cap.
You can measure the resistance: disconnect the transducer from the Sonic Speed box.
It should be 110 kilo ohm +-1% between red and black, infinite ohms to the screen.
Did the exchange job 2 months ago.
*. Aft transducer on the keel : translucent hose in the locker near the washing machine/freezer
* Forward transducer on the hull : grey pipe under the seat near the bathroom bulkhead
See the 2 pictures:
Detach ALL tie-wraps from the black transducer cables in the pipes to the Sonic Speed control box in the small cupboard
* firmly solder long extension cables to the old transducer cable ends
* drill holes in the center of the old transducers, fit self tapping screw
* pull the screw while someone inside the boat feeds the extended cable into the pipe
* important: leave the extended part of the cable in the pipe because you will use it to pull the new sensor in!
* clean and lubricate the pipe end where the transducer sits in the hull e.g. silicone grease.
* solder a new sensor to the extension cable and pull the new sensor in while someone at the other end of the pipe gently pulls the cables in.
I did the last point with the boat in the water as both pipes end well above the waterline.
My transducers are B&G part number 184-00-076/FI.
Good luck, this is less daunting than it looks....
sv Malaka Queen SM2k #348 @Monastir