Stiletto Performance Propellers • Extended Cup • High Rake • Progressive Pitch • High Strength Alloy • Precision Balanced. Performance and value, redefined from Stiletto. The unique high-rake, progressive pitch configuration is designed to help most boats achieve their best overall performance at all throttle levels... low end, mid-range and top end. Manufactured using a durable 15-5 ph one piece stainless steel casting, then polished to a gleaming mirror-like finish. Stiletto propellers are backed by a limited lifetime blade failure warranty. Your propeller is one of the essential links between your boat and the water. Please carefully choose the Stiletto propeller that will best suit your application. Yamaha Outboard:Yamaha V-4 and 3 cylinder outboards. For the Stiletto propellers above with the first digits of "ST313" - use Yamaha #688-45987-00-00 thrust washer or equivalent for 3 cylinder outboards and Yamaha #6E5-45987-00-00 for all other models. Important: These recommendations are for single engine installations only. For most twin engine installations, it is necessary to increase the pitch by 4".