Mercury - Floating Prop Wrench (9/16") Boater Tool Series Composite Material 859046M1. Overview. Every boater has dropped something overboard-usually something important. That quick gasp, the splash, and then the slow, sinking moment of regret. The Mercury Floating Prop Wrench 859046M1 saves you from that situation. It's light, it floats, and it makes swapping props on the water a whole lot less stressful. It's one of those tools you keep because it just makes sense.. Key Features. • Designed fo