Mercury - Flo-Torq SSR HD Propeller Hub Kit Heavy-Duty Propeller System Advanced Rubber Sleeve Design 8M0101601. Overview. There's a moment, right before you throttle up, when you can feel the whole boat waiting on the prop to grab water and go. When everything is tuned right, that transition is smooth-no jolt, no snap, just a clean surge forward. That's exactly the kind of assurance the Mercury Flo-Torq SSR HD Hub Kit brings to high-horsepower outboards. It's engineered for boats that work hard