Mercury - SpitFire X7 4-Blade Stainless Steel Propeller 12.8" Diameter x 21" Pitch Right-Hand Rotation 4-Blade Stainless Steel Polished Finish 8M0151364. Overview. When you're chasing open water speed and precision handling, few props make your boat feel as alive as the Mercury SpitFire X7 12.8x21 Right-Hand 4-Blade Stainless Steel Propeller (8M0151364). From the moment you throttle up, you can feel it crisp acceleration, confident grip, and a smooth transition from idle to plane. It's fast, res