Maybe a catamaran design.
for each side use (about 3-5) 4" pieces of PVC,
*edit:fill them with Great stuff before you glue the end caps.
-Tie them together tight at 4 or 5 places with nylon rope.
-Connect 4'x8' external plywood sections across them and tie the corners to the PVC through holes cut in the plywood.
-Add a thick board at the front center and rear of plywood.
-Flip it over and attach bearing like drive shaft bearings for cars or maybe wheel burrow bearings to the thicker wood boards.
-Find an axle (metal rod size that fits the bearings).
-Order a 1000cc sport bike engine from a totalled bike off Ebay.
-Remove the transmission and mount it sideways on the plywood.
-Find a propellor and ask them what RPM range it's for.
-Find a motorcycle sprocket that will give you that range but staying below redline of motor.
-Weld /mount sprocket to the axle rod.
-Cut a hole in the plywood and run the motorcycle chain around the sprockets.
-Go around and [obtain] all the solar panels off city stuff you can get.
-Get a few 4x8' pieces of that pink styrofoam at home depot.
-Glue them together, and mount the solar panels on top. You can coat them with fiberglass shetts and bondo and sand them if you wish.
-Tie it to the back with rope and run wires to an electric boat motor.
-Get an aluminum sail mast, the mounts and sail from a salvaged boat suitable., mount it to the deck.
-Build a cannon like mobile chernobyl's 10 gallon and mount it in front.
-Be careful not to get caught while being a pirate in your PVC Gas/ wind/ solar powered boat equipped with harpoon blaster etc.
8)
EDIT: Maybe the john boat is a much better idea(?)