Yankee is 100% spot on about the GT54/56 for trolling. I should have listened to him when I bought mine 3 years ago. It will track balls as long as it's flat calm. But anything more than a slight chop, you're in the dark! I went a different route and added a refurb Lowrance Elite 7 with a basic 2D 83/200 ducer that also networks with my TM. Couldn't be happier!