Bob,
The XPTH-9-HDSi-180-T transducer has been out for years now. It can use the 200kHz and 83kHz 2D sonar and the 455kHz and 800kHz Si sonar. This is the “HD” side imaging transducer for the 898c Si, 997c Si, 998c Si, 1197c Si, and 1198c Si units [it can also be used with the 797 and 798 units but they cannot use the 800kHz Si sonar frequency].
The older XTH-9-Si-160-T transducer came out with the 981c Si and 987c Si units. It can use the 200kHz and 50kHz 2D sonar and the 455kHz and 262kHz Si sonar. The 898c Si, 997c Si, 998c Si, 1197c Si, and 1198c Si units can fully use this transducer with a change to the Transducer Select menu [the 797 and 798 units can use this transducer as well but they cannot use the 50kHz 2D sonar or 800kHz Si sonar frequencies].
Both transducers are housed in a plastic Thru-Hull (reinforced) housing and have a shielded cable.
Your member information shows an 1157c as your unit, is this the unit you are trying to use with these transducers?