Cabelas has these decoy propellers that attatch to the decoys keel. You turn it on then drop the deek in the water. 3 of them do nicely and they're only about 12 bucks a piece. Only thin you have to watch out for is to make sure you have some good spacing between your propeller deek and the others or they will tangle up. Also shortening your deek chord helps this.
Here's the link.

http://www.cabelas.com/product/Hunti...3Bcat104290380