It looks like to me that scavenger uses a piece of auger conveyer as a prop. This is very common and as long as you know the inside diameter of the auger than you can order different sizes and pitches for this unit. You can order augers in both left and right rotation. I have to think that scavenger bores the inside of the auger shaft, to fit on there application. I think that if it was mine I wood get a piece of auger with more pitch and leave a bigger gap in-between the flitting. Just my thought on the situation, hope it helps.

that is what they use. only thing i can figure on the motor turned backwards is it was the easiest way to mount it. i didnt know you could get the auger in both hands. that was the other reason i guessed the motor was turned around. if so you could build an auger prop for any long tail? i have run the scavenger. the props are not very efficient but they handle rocks very well. this would be a good option for someone running rock rivers.