Yamaha - Shifter Lower Unit Shift Mechanism 6AX-45641-00-00. Overview. Shifting should feel clean and solid-no hesitation, no grinding, just straight into gear. When the internal shifter starts wearing out, that smooth feel disappears and you'll notice it right away at the helm. This is one of those parts that takes a beating every time you go from neutral to forward or reverse. Yamaha built this shifter to hold up under that constant use and keep your lower unit engaging the way it's supposed to.. Key Features. Positive Gear Engagement - Transfers shift input cleanly to help the lower unit engage without hesitation.. Factory-Precision Fitment - Built to Yamaha specifications for proper alignment within the shift system.. Durable Internal Design - Handles repeated shifting cycles under load without premature wear.. Smooth Operation Feel - Helps restore crisp, predictable shifting at the control handle.. Engine & Boat Compatibility. Designed for Yamaha outboard lower units that use this