Frequently Asked Questions


Engine Alignment Inboard...

How do I align my Inboard Engine?

Important: Engine alignment MUST BE RECHECKED with boat in the water, fuel tanks filled and with a normal load on board.

Engine must be aligned so that transmission and propeller shaft coupling centerlines are aligned and coupling faces are parallel within .003" (0.07 mm). This applies to installations with solid couplings, as well as flexible couplings.

  1. Check mating faces on transmission and propeller shaft couplings to make sure they are clean and flat.


  2. Center the propeller shaft in the shaft log as follows:

    • Push down and then lift the propeller shaft as far as it will move, then place the shaft in the middle ofthe movement.
    • Move the shaft to the port and then to starboard as far as the shaft will move, then place the shaft in the middle of this movement.
    • With the shaft in the center of the shaft log, align the engine to the shaft.


    • figure 1
      Figure 1. Center Prop Shaft


  3. Check that coupling centerlines align by butting propeller shaft coupling against transmission coupling. (Figure 2) Shoulder on propeller shaft coupling face should engage recess on transmission coupling face with no resistance.


    figure 2
    Figure 2. Coupling Flange Alignment


    Note: Some propeller shaft couplings may not have a shoulder on mating face. On these installations, use a straight edge to check centerline alignment.


  4. Check for any angular misalignment. Hold coupling faces tightly together and check for a gap between coupling faces with a .003" (0.07 mm) feeler gauge at 90-degree intervals (Figure 3).


    figure 3
    Figure 3. Angular Alignment