Viking, It will be tough to get a solar panel with enough current to charge a trolling motor. Ric's link shows a very good sturdy brand, the ICP, made in Canada. Fry's also sells them. They have several waterproof adapter cables with a variety of end connectors(alligator,ring lug, cig. lighter, etc. The 2 watt one will get you nothing. The 6 watt one will get you 400 millamps, meaning it will take 100 hrs to charge a fully discharged 40 amp hr, which is a small trolling battery.
The most watts per dollar comes from Harbor freight, and is 3 15watt panels in series for 45 watts. It includes a charge control panel. That is 3 amps charge rate and will recharge a partially discharged trolling battery on a bright summer day. 200 dollars. They have a 2 watt maintainer panel, sun visor clip on that can be used to trickle the other battery, if 12 volt. Or they have a 5 watt, which trickles at 350 milliamps.
