Mercury - Floating Prop Wrench (13/16") Boater Tool Series Composite Material 859046M2. Overview. A prop wrench is one of those things you hope you never need mid-trip-but when you do, you want it right there within reach. The Mercury Floating Prop Wrench 859046M2 brings that same sense of readiness, plus the peace of mind that comes from knowing it won't disappear into the water if you drop it. Light, tough, and easy to spot, it's made for boaters who like to be prepared.. Key Features. • Sized