[ursa minor]

The key point I was trying to make in my post above is that stainless allows for more advanced blade design. Things like the rake of the blades, skew in the blade that allows more effective control of pitch from the blade root to the tips and more aggressive cupping of the trailing edges of the blades to reduce tip losses. No question that a stainless propeller made in exactly the same manner as an aluminum one would have minimal or no performance difference.

The prop I'm running on the Whaler is optimized to run with the engine mounted higher on the transom. The reduction in drag from raising the gear case higher is probably the reason for the speed difference. The aluminum prop was probably cavitating with the engine raised up, it definitely ventilated in turns. It may have performed better with the engine mounted lower. This was all part of dialing in the new engine when we replaced the original engine a few years ago. Also, what I'm seeing on a relatively lightweight 17 foot skiff doesn't necessarily translate to a heavy deep V or a pontoon boat.