You should test-fit the transducer and cable before installation.
Allow a loose gap of at least 10 cm ( 4 in.) above and 10 cm (4 in.) below the rotating joint to create a loop in the cable. The loop must be large enough to allow full rotation of the transducer in both directions. Allow a minimum of 25 cm (10 in.) of cable to cover the 20 cm (8 in.) section between mounting points.
Use black electrical tape to secure the transducer cable to the shaft.
Test the full rotation of the trolling motor to ensure the cable clears the rotating joint and is not pulled tight due to tension during rotation.