It sounds like the boat motor or something else is blocking the upper part of the right Si sonar beam. Try raising the motor up the next time you are out in shallow water and see if that improves things or not. If not, try posting a screen snapshot of the Si View with the SI Range menu set to 20 feet. Also post some pictures of where you have the transducer mounted. We will need to see the overall back of the boat as well as pictures looking across the transom of the boat from right to left and left to right. These pictures should be taken at the same height as the transducer.