Check Shaft Alignment

• 1). Access the rear of the boat's engine compartment. Open enough access that the transmission and shaft are within easy reach. Look for the shaft coupler at the rear of the transmission. Clean off any rust or grease with a wire brush and rags.
  
  
• 2). Remove the bolts connecting the two halves of the coupler. Use the pipe wrench to hold the shaft if necessary. Separate the two halves of the coupler as much as space allows and use a wire brush to clean the face of each half. Inspect the face of the shaft coupler to identify the ridge on one half and the recess on the other. Ensure these surfaces are clean.
  
  
• 3). Bring the two halves of the coupler back together until the ridge is sitting in to the recess. Bring the two halves lightly against it so that a .015 inch feeler gauge can be slid in and out of the space with little force. Use the feeler gauge set to measure the gap between the two halves in four at 90 degrees apart. Ensure that these four gaps are equal. There should be no more than a .004-inch difference in the gap from one point to the point 180 degrees opposite.
  
  
• 4). Loosen and adjust the motor mounts on the front of the engine and on the transmission to bring the gap into specifications. Raise or lower the engine, or shift it from left to right as necessary to line up the shaft and transmission correctly. For example, if the gap is too large at the top of the shaft, lifting the front of the engine will bring it back in to specifications.
  
  
• 5). Tighten all engine mounting bolts, then measure the gap again to ensure nothing has changed while securing the mounting hardware. Reinstall the coupler bolts and tighten securely. Start the engine and check for vibrations and noise while in gear and at idle.