I have a Piranha, great concept. I used it on the Colorado river. I used it on a 21' Caliber1 w/350mag and it worked fine, even was able to tow a skiier. However the horsepewer is limited to 260. Just don't do any racing with it. On the other hand, tried it on my current 21' Laveycraft w/454 w/6 people on board and it didn't work at all, couldn't get on a plane, RPM's were through the roof. It couldn't handle the weight and larger size of the boat. Had to pull over and switch back to the stainless. What size boat and engine do you have? It's a great prop for smaller boats and perfect for river trips, it will save your drive from getting mangled if you hit a rock, blades will just sheer off. Also the blades will bounce back on a light strike as opposed to bending permanently like on an aluminum prop. wink <Mark>