Im looking to buy a fish finder for my pontoon boat. Ive been looking around and I cant make my mind up on what to buy. Id like to stay less then $400. I live in WV and will be fishing the Kanawha and Ohio rivers only. I want water temp. for sure. I was going to get one with a grey display until I saw the colored display models and I like them but they cost more. What about the GPS. Would I need a GPS or not. Any information on fish finders would be good.