Sierra Timing Belts provide extended durability and smoother performance characteristics required by today's marine engines. Key Features: Meets or Exceeds OEM Belt Specifications Modified Curvilinear Tooth Profile For Direct OE Fitment/Replacement Chemical and Contaminant Resistance for long life Additional Details: Material: Nitrile Const. For Maximum Durability Fiberglass Tension Member For Excellent Flex Behahavior Replacement Recommendation: Interval of 5 Years or 100 Hours of Use Fits Yamaha outboard enginesF25-F40