I use the SI transducer at the stern for the HB 997 mounted at the wheel. I use the universal transducer on the trolling motor for a HB 345c mounted up front. When I still had my F & F boat I used a switch to go back and forth from the TM transducer to the SI transducer with the 997. I let my son have that boat a couple of weeks ago. He has moved to White Hall because he works at NCTR which is at the arsenal. I am hoping he starts posting soon. His handle is "Blue Thunder"!