hey guys,
im doing a semester project for engineering where we have to build a boat that carries a navel orange around a pond.

there really is no restriction except that the boat cannot be store bought, and it cannot use human power at all, it also cannot be radio controlled and i know this is a r/c forum but i was hoping some of you could help me with the actual motor, prop, shaft, and battery side. oh and the spending limit is $80 total.

what do you guys suggest for a hull design? i was thinking maybe carving out styrofoam and coating the outside with fiberglass resin or bondo?

motor? only thing i have now is a "super speed hobby motor" from radio shack www.radioshack.com/product/index.jsp

prop and shaft? i was thinking maybe this? www.hobby-lobby.com/flexible_shaft_coupler_4mm_5mm_543_prd1.htm and www.hobby-lobby.com/10.2_prop_shaft_6mm_od_3_or_4mm_shaft_498_prd1.htm and www.hobby-lobby.com/50mm_r_104_prd1.htm

battery? what would be more powerful a 8-pack of AA (12 volts) or one of those r/c battery sticks 7.2V/2000mAH

also i think im just going to use a toggle switch for on and off.

my biggest concern is what kind of gearing it needs. would it be fine just for a direct drive from motor to prop or maybe get one of these? www.hobby-lobby.com/universal_marine_gear_drive_2.51_86_prd1.htm

what would be the best layout in the boat so the motor doesnt get yet but the prop is efficiently placed?

throw any ideas you guys have. any help would be greatly appreciated! remember budget is 80 bucks

thanks in advance!