Yamaha - Ring Gear Lower Unit Gear System 6AW-81891-00-00. Overview. Down inside the lower unit, the ring gear is doing the hard work of transferring power where it needs to go. When everything's dialed in, you get smooth rotation and solid push without thinking twice about it. But once wear starts or teeth get damaged, it shows up fast-usually with noise or rough operation. This is one of those core components you trust to hold up when the engine's putting real load through the system.. Key Features. Smooth Power Transfer - Works with mating gears to deliver consistent rotation through the lower unit.. Precision Tooth Design - Engineered for proper meshing and reduced wear during operation.. Heavy-Duty Construction - Built to handle high torque and continuous marine use.. OEM Fitment Accuracy - Matches Yamaha specifications for correct alignment and performance.. Engine & Boat Compatibility. Designed for Yamaha outboard lower units utilizing this ring gear configuration. Commonly used