Raymarine ST60 Owner's Handbook Manual page 22

Chapter 2: Maintenance and Fault Finding 9
CAUTION
If you need to remove the transducer insert, have the transducer
bung to hand and secure it in the transducer body immediately
after the insert has been removed, to prevent excessive ingress of
water.
If you are unable to rectify a problem, contact the Raymarine Product
Support Department or your own National Distributor, for assistance.