I just got off the lake and used my Echomap Plus 73sv for the first time. I have my transducer mounted on the port side, with a trolling motor on the starboard. Between the two is a 30 hp Evinrude, powering a 16 Lund. I normally run the motor in the first tilt slot, rather than all the way down. Being concerned about having tha same problem you experienced, I was hoping my normal running mode would be okay. It was, no darkened area, full view. To say I am amazed with the Garmin is an understatement. I am so glad I went out of my comfort zone and bought the Garmin. Try tilting you motor to that first knotch, see or you boat runs okay, and hopefully your SV will be corrected like mine was.