How to Line Up a Boat Engine
- 1). Check the shaft and coupling for radial run-out. Place a magnetic-base dial indicator on the motor bed or some other convenient spot and place the probe of the dial indicator on the shaft and the edge of the coupling. Rotate the shaft by hand or with a large pipe wrench and watch the dial indicator for movement. Remove and straighten the shaft if more than .005 inch of run-out is indicated.
- 2). Loosen and remove the coupling bolts (or bolts and nuts) with wrenches. Observe the coupling faces for relative motion as the bolts are removed. The shaft springing to create a large offset at the coupling halves indicates very poor alignment.
- 3). Lay a straight edge or machinist's rule across the edges of the coupling halves to check for lateral and vertical alignment.
- 4). Loosen the motor-mount bolts with wrenches. Leave a few threads engaged to retain all of the motor-mount hardware and shims while giving the mount slack to allow it to move around.
- 5). Add or remove shims to the motor mounts and jack the engine around with a pry bar as necessary until the edges of the coupling halves perfectly align both vertically and horizontally.
- 6). Pull the coupling faces to within roughly 0.010 inch. Check between the machined faces of the coupling halves with a feeler gauge. Add or remove shims to the motor mounts in small increments, as necessary, until the coupling half-machined faces are within .005 inch of being parallel to each other.
- 7). Tighten the motor mount bolts securely.
- 8). Check the offset and alignment at the coupling to ensure that nothing was disturbed while tightening the motor mounts. Repeat Steps 1 through 7 if adjustments are necessary.
- 9). Install the coupling bolts and tighten them securely with wrenches.
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