Mercury - Thunderbolt Propeller High-Performance Series High-Polished Stainless Steel QS5008X. Overview. There's a moment every boater knows-the quiet breath before you push the throttle forward. You feel the hull settle, the wheel straighten, and the engine waits for your signal. When you're running a propeller that you trust, that moment isn't tense. It's exciting. The Thunderbolt propeller creates that kind of confidence. It grabs the water cleanly, lifts the boat without hesitation, and stay