I used Piranha composite propellers on my twin Honda 40s for about 5,000 of the 7,000 miles of my great loop trip, and was very satisfied. I kept close track of my gas mileage, and figure the Piranhas saved me about half a mile per gallon, and gave me a knot or two top end over the original aluminum propellers. Though I never broke a blade, they're individually replaceable, and each blade costs about $18. According to the manufacturer, if you do hit something, they're easier on your drive train than stainless steel. The composite will shatter, preventing the force of the impact to be passed on to the drive train. Last fall I did a trip up the Wolf River in Wisconsin, where I live, in very shallow water. I did hit something big enough to knock the depth sounder off its mount. One blade on one of the engines shows some slight indication of damage, not enough to replace.