The presence of rust would be the result of not having the drain (unshielded) wire properly grounded. Although the rust can be cleaned off, if the drain wire remains not grounded properly, the rust will continue to accumulate.
Rust on the MEGA 360 or MEGA Live wet switch can cause a few major issues for the transducer.
- Prevent the wet switch from detecting water.
- Cause the transducer to show as "Unconnected"
- Cause irreversible damage to the transducer resulting in repair/replacement being necessary.