Fish Finder

I am looking into purchasing a fish finder "The Cuda" $100-130 range from the Fishin Hole or Crappy Tire I was just wondering if anyone has pro's and con's, I have a 12ft boat and will be fishing around the Brooks area (Newell being the biggest lake). Also when the catalogue says permanent does that mean that the head unit can't be removed or just the Trans. and such. Any Help is great, Thanks.