I have a 1197 with the transducer mounted in the step on the transom. I know you can mount an XP 9 20 transducer in the hull for high speed depth readings. Will an XTM 9 QB 90 T Quad Beam transducer do the same thing and a little more because it's a Quad Beam? Will a splitter cable recognize the Quad Beam?

Don't think so since the quad uses 455 kHz for the two sides and there is no electrical path with the Y cable on the 2D side for the two 455 kHz beams in the quad. The 455 kHz connection stays with the SI transducer using the Y cable.

You can use the transducer switch TS2 W and change the unit transducer selection each time you switch transducers.