Yamaha Lower Unit Assembly - 2 - 6A1-45300-03-4D - See Description for Applicable ModelsYamaha Lower Unit Assembly Complete Lower Unit System 6A1 45300 03 4D Overview When a lower unit is dialed in, the whole boat just feels rightsmooth throttle response, clean shifts, and solid push through the water. But when one starts to go, youll hear it and feel it fast, whether its noise, vibration, or rough engagement. This is the kind of replacement you go with when you want everything back to factory feel without piecing together internal