The SI pulses have to see left and right. If you have motor lower units blocking the SI pulses, it makes no difference where on the transom you put the transducer. SI covers from the water's surface to past vertical under the transducer on both sides.
If you did not exchange the included Compact SI transducer XNT 9 SI 180 T, you will not get as sharp of an image as you would with the HDSI transducer XHS 9 HDSI 180 T.
You have to be around fish to see fish. If you want to somewhat determine size, use the FishID with 2D sonar.
Use a SI RANGE setting that is three times the depth to get the best details for small stuff in water deeper than 20', in shallower water, a 50' SI RANGE works well.
This is bass with a very large school of 2"-3" shad: