You will find a lot of ansers here Humminbird Sonar/GPS as it is a problen that Humminbird is having. I have 2 Helix 10" and a 9" on my boat and the problem is more then just being caused by a double image. My favorite crappie lake has a max depth of 17' and my AutoChart has recorded areas 90' deep. There is updated info on that site giving a bunch of settings to use. Humminbird CS has not been a help as everyone has tried everything they say with no improvement. We are hoping for a software fix some day. We used to adjust out sounders for that second return as it gives a better image of the bottom. It is not right to have to dummy down a unit to fix a problem that we never had before. Don