I have two Garmin 1243XSV chartplotters. One is connected to a Garmin GT56UHD transom mounted transducer, but the other reads bottom off my old Airmar thru hull transducer. I like having the Airmar as a backup and it still provides a good bottom picture and the same depth readings as the state of the art unit. It’s also more resilient to damage than a transom mounted transducer.