I don't think you can go wrong with any newer FF from the better brands (hummingbird, Lowrance, Garmin...). On my old gheenoe I used a cheap Eagle Cuda 165 from wally world, and did the shoot through the hull method for the transducer. I was surprised how accurate the depth reading was, it really worked well. The newer machines work much better and mark more accurately, as technology advances better products get easier to afford.
PS if you do shoot through the hull the temp reading won't work, but I never needed it anyway.