Yamaha - Gear - 68T-45571-00-00Yamaha Gear Lower Unit Drivetrain Component 68T 45571 00 00 Overview This is one of those gears that takes constant load every time youre on the throttle. Its buried inside the lower unit, but its doing the heavy lifting when it comes to transferring power cleanly to the water. When everythings right, you wont hear a thingjust smooth, steady performance. When it starts to wear, though, it shows up fast with noise or rough operation you cant ignore.