Howdy! Need a little help on what Minn Kota Trolling Motor to buy for my 18ft. Grumman Deck Boat. What I want to buy, is a Minn Kota Power Drive, Auto Pilot, with Copilot added on. My boat currently, has a Johnson 12/24 volt 41lb. thrust with 6 speeds, foot control and seems to work the boat nicely! Want to know if I should go 12 or 24 volts, what thrust amount I might need, and if there is a better place to purchase for warranty and cost? Thanks for any info. Lare.