Mercury Prop 15.50R37 15D - 48-8M0003770. The Mercury Prop 15.50R37 15D (Part #48-8M0003770) is a high-performance stainless steel propeller designed to enhance acceleration, fuel efficiency, and top-end speed. With a 15" pitch and a 15.50" diameter, this right-hand rotation prop delivers balanced power and precision for a variety of boating conditions.. Key Features. Genuine OEM Mercury Propeller - Factory-tested and built to exact specifications for reliability and longevity. Premium Stainless