Could we see a screen snapshot of the Si sonar with the SI Range set to 20 feet?
Also some pictures of the transom area of your boat, especially one looking across the transom from the right to the left side at the same height as your transducer (and vice versa). I think that you are saying that you are getting some type constant left Si sonar return, which is usually due to some sort of physical blockage/reflection of the left Si sonar. It could also be the transducer itself, so if you could cross-test your unit with someone else that has a Humminbird Si unit (any model Si unit) it would help.