Twin Disc MG-5170DC, Service Manual

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175
Twin Disc, Incorporated
Installation
Marine Transmission Service Manual #1020667
When a heavy boat is dry-docked, it naturally undergoes some bending.
Therefore, it is always good practice to unbolt the marine transmission coupling
to prevent bending of the shaft.
With the engine and transmission in position on the engine bed, arrangements
must be made to have a controlled lifting or lowering of each of the four
corners of the engine. If threaded holes are provided in each of the engine
mounts, jacking screws can be used in them. The engine can be raised by
screwing down, or lowered by backing off on the jacking screws to obtain the
desired adjustment.
Steel plates must be inserted under the jacking screws so that the bolts will
not damage the engine bed. Lifting can also be accomplished by the use of
chain hoists or properly placed jacks. Adjustable shims also are available and
can simplify the alignment process, particularly for future realignment.
It may also be necessary to move the engine and transmission to one side or
the other on the engine bed to obtain horizontal alignment. This can be done
with a jack placed horizontally between the engine and the foundation. At the
same time, a straight edge is laid across the edges of the flanges at the top
and side to check the parallel alignment of the coupling edges.
Figure 143. Checking Parallel Alignment of the Coupling