You don't have enough torque for that much blade area if it is a 3 or 4 blade. The reason the indigo rev's up is the blade area is matched to the torque of the A-4.
The 12 x 7's you here of on the A-4's are almost all 2 blade props. I ran the Indigo on my E35MKII and it worked great in all conditions.
And if you're racing you'd do better with the 3 blade rating than the feathering with that big ball dragging through the water.
Dave Neptune
