My transducer in mounted about 3" down from the water line on my boat, I had to locate it on the port side on the outside edge, in about 4" on the transome because for some reason I had alot of interferance, why I don't know, at an idle it was fine but trolling speed it showed fish eveywere,and at running
speed it would lose the bottom, showing 600ft at times, so I moved it to it's
position now and it's fine so that would make my situation 3" more of water than what I'm reading, am I thinkig right or not, Don't hesitate to correct me if I'm wrong, Because I'm going to up grade my finder and don't want to make this mistake again!! Thanks PAP