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Supports
between
the
bed
stringer
and
extending
out
from
the
stringers out to the hull may be required for proper support and to
aid in the absorption of vibrations.
PROPELLER COUPLING
Each Westerbeke Diesel engine is regularly fitted with a suitable
coupling connecting the propeller shaft to the engine.
The coupling must not only tr ansmi t
the power of the eng ine to
turn the shaft,
but must also transmi t
the thrust ei ther ahead or
astern from the shaft to the thrust bear ing which is built into the
reduction gear housing of the engine.
This coupling is very carefully
machined for accurate fit.
For all engine models, a propeller half-coupling, bored to shaft
size for the specific order, is supplied.
The coupling either has a
keyway with set screws or is of the clamping type.
The forward end of the propeller shaft has a long straight keyway.
Any burrs should be removed from the shaft end.
The coupling should
be a light drive fit on the shaft and the shaft should not have to be
scraped down or filed in order to get a fit.
It is important that
the key be properly fitted both to the shaft and the coupling.
The
key should fit the side of the keyway very closely, but should not
touch the top of the keyway in the hub of the coupling.
If it seems difficult to drive the coupling over the shaft, the
coupling can be expanded by heating in a pail of boiling water.
The
face of the propeller coupling must be exactly perpendicular to the
centerline or axis of the propeller shaft.
PROPELLER
The type and size of propeller varies with the gear ratio and must
be selected to fit the application based upon boat tests.
To utilize
the full power of the engine, and to achieve ideal loading conditions,
it is desirable to use a propeller which will permit the engine to
reach its full rated RPM at full throttle under normal load.
ALIGNMENT OF ENGINE
The engine must be properly and exactly aligned with the propeller
shaft.
No matter what material is used to build a boat it will be
found to be flexible to some extent and the boat hull will change its
shape to a greater extent than is usually realized when it is launched
and operated in the water.
It is therefore very important to check
the engine alignment 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 misalignment 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 couplings can be
brought together without using
force
and so that
the flanges meet
5
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