Mercury - Floating Prop Wrench Propeller Tools Composite Floating Design 859046M4. Overview. There's something reassuring about having the right tool within reach when the water gets a little choppy or a prop takes a hit. This Mercury Marine part is one of those pieces you don't think about until the moment you really need it - and then you're grateful it's there. The Floating Prop Wrench 859046M4 gives boaters a calm sense of control, the kind that comes from knowing a simple prop change won't