I would assume i am not the first person to try and use their transom mounted transducer for ice fishing. I have done some searches online and it sounds like the trick is mounting the transducer to something that be stuck down the hole and keeps the ducer level.
Where do you set your transducer when ice fishing? I see plenty of guys with a couple of feet of cord out or more. Must be trying to set below the ice. Typically set mine with less than a foot of cord out and then just position it in the center of the hole. Have had at times in really shallow water the top of the transducer barely under the surface of the water. In this situation it really needs to be centered in the hole to not read the ice.