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S
ECTION
surface of the object. In the case of the propeller,
such damage is sometimes called a "burn." It may
be caused by an irregularity in the propeller's leading
edge, and it should be corrected by reconditioning
the propeller or by replacement.
Cavitation is a normal occurrence in modern sport
boats, and prop inspection should be part of routine
maintenance.
P
T
ROPELLER
ORQUE AND
Some of the more powerful motors create a
considerable torque effect; that is, a twisting motion
causing the boat to ride with one sheer lower than
the other. This twisting reaction is caused by the
direction of propeller rotation lifting one side of the
boat. This causes an uneven drag, so that a boat's
bow may tend to fall off in one direction or the other
from the intended course given by the wheel.
Torque action may occur when maximum or close
to maximum rated horsepower is applied. Any slight
torque may be offset by shifting passenger or gear
weight laterally to the high side of the boat.
C
-
P
OUNTER
ROTATING
ROPELLERS
On twin engine yachts, one propeller turns in a
clockwise direction while the other turns
counterclockwise in order to maintain a straight
course through the water.
When removing or replacing propellers, be sure to
install the correct propeller on the correct drive.
C
-R
P
OUNTER
OTATING
ROPELLERS
(F
. 4.10.1)
IG
4.10
4 • B
ILGE
I
C
TS
ORRECTION
& U
NDERWATER
P
I
ROPELLER
NSTALLATION
For proper rotation, the installation of propellers on
inboard engine boats requires the right hand
propeller to be installed on the starboard side and
the left hand propeller to be installed on the port
side. Install in the following manner:
Step 1: Inspect shafts
and propellers to
ensure the taper,
keyways, keys, prop
nut, jam nut and cotter
pin meet specifications.
Special attention
should be paid when
confirming key fit.
Key must fit snug in prop hub and propeller shaft.
Key must fit flat in bottom of both. If the key
radius does not match keyseat properly, stress
risers and catastrophic failure could occur.
•
Inspect propeller(s) to ensure the bore, diameter
and pitch meet specifications for specific engine
installation (diameter and pitch are stamped
on the side of prop hub).
Step 2: Dry fit the
propeller on the taper
without the key and
mark the position on
the shaft with a
permanent marker.
The
distance
between the prop
and the strut shall
never exceed one (1) shaft diameter.
•
Remove the propeller and insert the key, rotate
the shaft so the key is top dead center.
•
Using a clean rag, wipe the bore of the propeller
with a small amount of penetrating oil.
•
Apply a consistent coating of Prussian blue
compound to the surface of the shaft taper. The
application should be consistent and have a wet
film thickness of 2 mils. (similar to a light coat of
polyurethane).
G
EAR
:
®
52 Sundancer
(525 Sundancer
®
)
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