One of these sure would go well with the unit.
Composite LPG Tank
It's a composite propane tank that weighs 7.5lbs empty and holds 11lbs of propane. 18.5lbs total weight for the tank (when full) is much lighter than the motor itself and light enough to pass down by hand to the dinghy. No steel to rust all over your dink either.
11lbs of propane would give you 11hrs of motoring wide open and 26.5hrs at 1/2 throttle. The tank is also see-through so you can easily assess your fuel level.
I think I'm going to end up going the propane route.....