I just wanted to add a couple of things. Deacon, it doesn't matter if you spend $2500 on a unit. You might not ever know that there are fish in the area! I use my depth finder for exactly that. Depth and contour. It lets me know how deep the water is which will help determine my presentation. It also shows me underwater structure, which is one the most helpfull things of all!

Sonny, the Lowrance does run on a mototcycle battery. But some of those batteries are so small now. I have a full size trolling battery and I have a small battery for my graph. I bought it on E-Bay. It weight 7 lbs and approximate measurements are 7"L x 5"H x 4"D. The reason I chose this battery is it is totally sealed. Not like the 'sealed' batteries at Wal-Mart. It's guaranteed to not leak. There are no openings on it anywhere and it can be mounted in any position except upside down. But I did leave it upside down for about an hour once to see what would happen. Nothing! That way I have no fear of getting acid on anything I fish with. Especially my boat! I also keep my trolling battery inside a battery box on my boat to avoid any leakage.