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Frequently Used Boat Prop Terms

by Todd Alan

If you have never needed to look for a boat propeller in the
past, and have only started out, all the jargon that is
associated with a boat prop can leave you quite confused.
However, once youve familiarized yourself with the
associated language, looking for a boat prop can be quite

A boat propellers parts: Most commonly available boat props
usually have three blades or four, and these blades are
placed around the hub. The hub goes on to connect the
propeller blades and the drive shaft. A boat moves forward
due to the angle at which these blades are placed which
gives them the ability to screw through water. The end of
the prop blade that cuts through the water is referred to as
the leading edge, and the other end is called the trailing

The drive shafts teeth are referred to as splines, and these
arent part of the propeller itself. A hubs design ensures
that it fits into a drive shaft keeping in view the number
of splines it has.

Various Features: A boat propeller is mainly classified
depending on its diameter as well as pitch, and this is
normally embossed on the hub in the form of two numbers (in
inches). While the first refers to the propellers diameter,
the second refers to its pitch. The diameter of a propeller
is the distance from the end of the blade to the center of
the hub. The pitch is used in referring to the distance that
can theoretically be traveled by the propeller in one
revolution. The reason that a pitch is referred to as a
theoretical representation is because it can experience
slips in different scenarios. Slip refers to the ratio
between the actual distance traveled and the props pitch.
The slip could be different under similar environments; for
instance while a work boat might experience a 60% slip, a
well kept private boat might experience a 15% slip in
exactly the same weather conditions. 

The rotation can be either left or right hand. A majority of
the boat props have right hand rotation. You can expect to
find a left handed one on engines wherein double engines are
needed to counter the motors torque which can lead to
pulling the steering in one direction.

Cupped blades refer to blades whose angles have been
specially treated and their trailing edges are further
curved. This is done because it increases the props
performance under specific circumstances.

Rake is used to describe the angle of the blade from where
it connects with the hub. Negative rakes indicate forward
pointed blades, and this is usually done to add strength to
high end propellers.

Before you start, it is important that you note down your
engines specifications, such as make, horse power (HP),
model, etc. and your existing props details like its
material (steel, aluminum, etc), diameter, pitch, and number
of blades. You can then comfortably embark upon your hunt
for a new boat prop. - 920

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