Material
Though aluminum and even plastic are used to make
props, the choice for bass boats is stainless steel. Achieving
maximum performance in a large rig through aluminum is
likely impossible, since the material flexes and is less efficient
at propelling the boat forward at the proper rate for the cho-
sen prop – the result being what engineers refer to as “slip.”
For that reason, prop engineers have strived to use
the hardest, strongest steel alloys for prop
design, allowing the most aggressive shaping
and best performance with the least
amount of slip.
RPM and WOT
The first step in choosing the best
prop is to determine your motor’s prop-
er RPM range at wide-open throttle
(WOT). Engine manufacturers make this
information available online with simple
prop-selector tools. Once the WOT RPM
range is determined, the goal is to obtain
maximum speed and performance in that
range, which sometimes requires trial and
error with different props.
Diameter and Pitch
To dial in the right prop for your boat’s WOT RPM
range, you need to understand how high-perfor-
mance props work. Bass boat propellers are cate-
gorized by two basic measures: diameter and pitch.
The diameter is the measurement of the inside
hub, and, for the most part, the smaller the diame-
ter, the faster the prop will spin. Pitch is primarily
controlled by blade size and shape, and is a meas-
urement of the forward travel
distance per revolution of
the prop in a solid (no-slip)
medium. For instance, a
27-pitch prop should trav-
el 2 inches farther than a
25-pitch prop given the
same power, load, drag, etc.
Therefore, given the same
RPM, a prop of larger pitch
will push a boat faster. That
same larger size requires
more power to spin,
though, so the proper bal-
ance of pitch and RPM
must be obtained.
Blades
Another major prop vari-
able to consider is the number
of blades. For the most part, the
more blades, the more bite, and
therefore quicker response in the boat.
OCTOBER 2017 I FLWFISHING.COM
Props with four (or occasionally five) blades typically turn
sharper and help the boat plane off faster, and can keep a
boat on plane at lower speeds and in winding turns.
However, with an added blade comes more drag in the
water, and often an overall reduction in speed.
A three-blade prop has less drag and traditionally pro-
duces a higher top-end speed.
The three-blade-versus-four-blade decision is
more complicated these days due to the size of
bass boats and corresponding increase in
water draft. Engineers call this “increased
wetted area.”
With more wetted area, drag is sub-
stantially increased, requiring even
more propeller engineering ingenuity.
For these circumstances, outboard
manufacturers are again turning to
four-blade models to lift the boat bet-
ter. By utilizing an additional prop
blade, the boat is lifted higher, the
waterline is pushed back and drag is
reduced. If you’re operating at the correct
RPM range at wide-open throttle, but can’t
seem to get proper speed, water drag might be
your problem, and a four-blade prop might help.
Advanced Engineering
In 2008, Mercury introduced the first modern hybrid prop
with its Fury line of three-blade props designed for both speed
and control. Though cutting-edge at the time, its concept is the-
oretically simple. By reducing the hub diameter of a traditional
three-blade prop, the new model is able to “spin up” faster, pro-
ducing quicker response. By maintaining three blades overall,
drag is minimal and top-end speed isn’t sacrificed.
Another method for increasing spin is to control
exhaust. The outboard motors used on bass boats
release motor exhaust through the prop hub and
out the rear. By allowing a portion of that
exhaust to exit sooner, the water in contact
with the prop becomes aerated, and the
prop can spin more easily. This helps pro-
duce immediate lift, also known
as “hole shot,” in the boat.
Most high-end stain-
less props offer some
sort of exhaust ports.
Evinrude has taken the
concept one step further
with its Variable Vent Ports
(VVP) on the Raker H.O. prop
line. Boat owners can tweak
the exact amount of ventilation
offered through the prop hub
to match their personal boat
and load dynamics best.
Need more prop spin?
Start opening ports.
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