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 TM 55-1905-219-14-4
3-53.
PROPELLER SHAFTS - MAINTENANCE INSTRUCTIONS (Continued).
LOCATION
ITEM
ACTION
REMARKS
ADJUSTMENT (Cont)
NOTE (Cont)
(3) Then the marine gear flange coupling is rotated 90, 180, and 270 degrees with the
feeler blade being moved around the flange again in each successive position. If the
alignment is correct, the feeler gauge will fit snugly, with the same tension, all around the
flange coupling.
(4) If the alignment varies during rotation, then further alignment is necessary, or the
marine gear and shaft couplings could be checked for improper face runout. Face runout
on the marine gear output flange can usually be corrected by repositioning the coupling
on its spline. Shaft coupling runout is usually due to an inaccuracy of taper fit or key
(5) Some boats are not structurally rigid and some carry their load in such a way that
they will "hog" or go out of normal shape with every loading and unloading. Where this
condition exists, it may be necessary to make a compromise between the top and bottom
coupling clearance by leaving a greater clearance at the bottom of the marine gear
output flange and propeller coupling. This clearance might be 0.005 to 0.007 inch (0.
013 to 0.018 cm) while the top would maintain the standard 0.002 inch (0. 005 cm).
(6) During the process of securing final alignment, it may be necessary to shift the
engine many times. When the final alignment is secured, the necessary steel or
hardwood shims are made up and the engine and gear is fastened in place. The
alignment is then rechecked. and if satisfactory, the coupling is bolted together.
(7) When a heavy boat is dry-docked, it naturally undergoes some bending. Therefore, it
is always good practice to unbolt the marine gear coupling and prevent bending of the
shaft.
3-982
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