Mercury - Thunderbolt Propeller High-Performance Series High-Polished Stainless Steel QS5004X. Overview. There's a certain calm that settles in when you know the propeller beneath you is built to handle the kind of water you love running. Whether you're pushing out toward an offshore reef or cruising back toward the slip with a day's worth of stories, a prop like the Thunderbolt gives you that steady reassurance. It's the feeling of knowing your boat will respond every time-clean, predictable, a