The Sting Ray XRIII is designed with a new sleeker hydrodynamic profile for the fastest hole shot yet. This unique design mirrors the tunnel-prop technology of offshore superboats. By capturing the prop wash, the XRIII harnesses its power for added thrust. You'll enjoy better performance and greater fuel savings. The XRIII also utilizes a vice-block 3-point locking system for easy no-drill installation. No more measuring. No more templates. No more damage to your engine. For engines up to 300 hp.