Yard Sales and ebay are the places to find bows. It doesn't need to be anything nice. They take a beating it the boat any way. The best poundage is 35-45 lbs. I like about 45 lbs. Too much poundage and you start to lose arrows in roots, logs, and mud. My buddy shoots everything with a 35 lb kids bow and he loves it. I shot about a 45 lb golden eagle, but I just got a 40# recurve to play with.
Good luck