Fast Build Scale Model

I will be interested in your outboard design, I took a look at it 15years ago. The problems then were, I needed a cheap airfoil about 2" cord that could take 2 or 3 kg. thrust and a set of small diameter 90 degree gears for the prop shaft. At the time I could not find the airfoil and didn't want to build one. I did find some pressed metal gears form RC 'Pan" cars that might work.
Today maybe a hollow helicopter blade may work for the foil leg?

 

I am going to build the assembly he way I built slot cars - soldered copper tube and sheet. Then I will cover it with epoxy balloons, sand it to shape and final epoxy coat.

I don't think the accuracy of the foil is critical as most of it is out of the water.

 

This might be even easier,
http://oxe-diesel.com/the-transmission/
using belt drive components from R/C cars.

 

yeah, belt drives have an appeal, but the engineering to support them is more difficult. In a model, getting a belt drive to drive the prop makes the shaft build more difficult.