I have the 997c SI. When the si is set to 800khz the right side is much darker then the left, and not very clear resolution. I switched to 455khz and the picture is much clearer, but the left side is slightly darker. I SLOW troll, about .4-.6 mph. I do have the screen speed set at 2. If I slow it to one will that further sharpen my picture?

By the way love the unit, I can see my homemade cover as if it were on a black and white tv.

UT