A. Blade Tip
The maximum reach of the blade from the center of the
propeller hub. It separates the leading edge from the
trailing edge. (UP)
B. Leading Edge
That part of the blade nearest the boat, which first cuts
through the water. It extends from the hub to the tip. (UP)
C. Trailing Edge
That part of the blade farthest from the boat. The edge
from which the water leaves the blade. It extends from
the tip to the hub (near the diffuser ring on through-hub
exhaust propellers). (UP)
D. Cup
A small curve or lip on the trailing edge of the blade,
permitting the propeller to hold water better and
normally adding about ½&#quot; (12.7 mm) to 1&#quot; (25.4
mm) of pitch. (UP)
E. Blade Face
That side of the blade facing away from the boat, known
as the positive pressure side of the blade. (UP)
F. Blade Back
The side of the blade facing the boat, known as the
negative pressure (or suction) side of the blade. (UP)
G. Blade Root
The point in which the blade attaches to the hub. (UP)
H. Inner Hub
This contains the shock absorbing hub (described below).
The forward end of the inner hub is the metal surface
which generally transmits the propeller thrust through
the forward thrust hub to the propeller shaft and in
turn, eventually to the boat. (UP)
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I. Outer Hub
For through-hub exhaust propellers. The exterior surface
is in direct contact with the water. The blades are
attached to the exterior surface. Its inner surface is in
contact with the exhaust passage and with the ribs which
attach the outer hub to the inner hub. (UP)J. Ribs
For through-hub exhaust propellers. The connections
between the inner and outer hub. There are usually three
ribs, occasionally two, four, or five. The ribs are
usually either parallel to the propeller shaft
("straight"), or parallel to the blades
("helical"). (UP)
K. Flo-Torq™
Shock-Absorbing Rubber Hub
Rubber molded to an inner splined hub to protect the
propeller drive system from impact damage and to flex
when shifting the engine, to relieve the normal shift
shock that occurs between the gear and clutch mechanism. (UP)
L. Diffuser Ring
Aids in reducing exhaust back pressure and in preventing
exhaust gas from feeding back into propeller blades. (UP)
M. Exhaust Passage
For through-hub exhaust propellers. The hollow area
between the inner hub and the outer hub through which
engine exhaust gases are discharged into the water. In
some sterndrive installations using a through-transom
exhaust system, this passage carries air. (UP)
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