Westerbeke WPDS-20 Technical Manual page 10

ment at frequent intervals and to correct
any errors when they may appear.
Misalignment between the engine and the
propeller shaft is the cause of troubles
which are blamed often on other causes.
It will create excessive bearing wear,
rapid shaft wear and will, in many cases,
reduce the life of the hull by loosening
the hull fastenings. A bent propeller
shaft will have exactly the same effect
and it is therefore necessary that the
propeller shaft itself be perfectly
straight.
One particularly annoying result of mis-
alignment may be leakage of transmission
oil through the rear oil seal. Check to
make sure that alignment is within the
limits prescribed.
The engine should be moved around on
the bed and supported on the screw-jacks
or shims until the two halves of the coup-
lings can be brought together without using
force and so that the flanges meet evenly
all around. It is best not to drill the
foundation for the foundation bolts until
the approximate alignment has been accu-
rately determined.
Never attempt a final alignment with
the boat on land. The boat should be in
the water and have had an opportunity to
assume its final water form. It is best
to do the alignment with the fuel and
water tank about half full and all the
usual equipment on board and after the
main mast has been stepped and final rig-
ging has been accomplished.
Take plenty of time in making this
alignment and do not be satisfied with
anything less than perfect results.
The alignment is correct when the shaft
can be slipped backwards and forward into
the counterbore very easily and when a
feeler gauge indicates that the flanges
come exactly together at all points. The
two halves of the propeller coupling
should be parallel within 0.002 inches (A).
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In making the final check for alignment,
the engine half coupling should be held in
one position and the alignment with the
propeller coupling tested with the propeller
coupling in each of four positions, rotated
90
0
between each position. This test will
also check whether the propeller half coup-
ling is in exact alignment on its shaft.
Then, keeping the propeller coupling in one
position the alignment should be checked
rotating the engine half coupling to full
position each 90
0
from the next one.
The engine alignment should be rechecked
after the boat has been in service for one
to three weeks and, if necessary, the
alignment remade. It will usually be
found that the engine is no longer in
alignment. This in not because the work
was improperly done at first, but because
the boat has taken some time to take its
final shape and the engine bed and engine
stringers have probably absorbed some
moisture. It may even be necessary to re-
align at a further period.
The coupling should always be opened up
and the bolts removed whenever the boat is
hauled out or moved from the land to the
water, and during storage in a cradle.
The flexibility of the boat often puts a
very severe strain on the shaft or the
coupling or both when it is being moved.
In some cases the shaft has actually been
bent by these strains. This does not apply
to small boats that are hauled out of the
water when not in use, unless they are
dry for a considerable time.
EXHAUST SYSTEM
Exhaust line installations vary consid-
erably and each must be designed for the
particular job. The general requirements
are to provide an outlet line with a mini-
mum of restrictions and arranged so that
sea water, rain water, or condensation
cannot get back into the engine. There
should be a considerable fall in the line
between the exhaust manifold flange and
the discharge end. This slope in the pipe
makes it difficult for water to be driven
in very far by a wave; and a steep drop
followed by a long slope is better than a
straight gradual slope. Avqid any depres-
sion or trough to the line which would
fill with water and obstruct the flow of
exhaust gas. Also avoid any sharp bends.
Brass or copper is not acceptable for
wet exhaust systems, as the combination of
salt water and diesel exhaust gas will