Solas Propeller is a premier name in the boat propeller industry with focus on design quality and manufacturing expertise. The company was founded in 1985 and since that time has provided the marine industry with trusted propellers for their watercraft which includes the Rubex Propeller System line as well as their stainless and aluminum propeller lines, including Amita, Titan and Saturn featuring the pressed in hub system.
Solas Boat Propellers are leaders in the industry because they are precision made with top-notch materials, balanced and ready to give you the performance you need. The result of their engineering is a stronger, yet thinner blade that is smooth, yet tough and designed for efficiency. These propellers come with a pressed in rubber hub, so there is no need for an additional hub kit.
Solas propellers come in either aluminum or stainless for your specific needs, but what is the difference and what should you consider when choosing?
The Rubex Propeller System also consists of your choice of either a top quality stainless steel propeller or aluminum propeller with a rubber interchangeable hub. The system, in either aluminum or stainless, is the answer to less chatter and vibration.
The Solas Rubex rubber hub has an advantage over plastic hubs as it resists deterioration. It has a 10% deflection rating to give you softer shifting and reduce propeller shaft shock should the propeller strike an object. The Rubex hub is designed so as to not spin in the propeller and can be used with another propeller, should your current propeller blade become damaged and require replacement.
By Neil Mullen
Recent advantages in outboard technology have
made choosing the correct propeller for your boat
both easier and more difficult--easier because the
number of choices has doubled, and harder, for the
same reason. Propeller manufacturers have been busy
developing new 3-blade and 4-blade products and
size ranges of stainless steel propellers to meet
a growing number of hull types and horsepower ranges,
especially for 4-stroke engines.
Four-stroke engines are designed to run at very
specific RPMs, so pitch sizes have become available
in 1 inch increments and new designs have appeared,
each more tailored to a specific hull type and application.
Propellers with higher rake angles and some with
more surface area have been developed to maximize
the power delivery of the 4-stroke torque curve.
The two most important things to remember in
choosing a propeller are that it meet your individual
needs for your individual application and that
it allow the engine(s) to run within the specified
RPM range at full throttle. Each boater and fisherman
is trying to meet his requirements, but they can
vary a lot.
What’s important to you and the way you fish:
Top Speed, Cruising Speed, Hole Shot, Load Carrying,
Slow-Speed Handling, Slow Trolling, Fast Trolling?
Two identical boats with identical engines could
be propped quite differently, depending on the
usage, water conditions, and load. There is no
such thing as the best or ideal prop for all applications
of a similar nature. Acceleration may be compromised
for top speed and fuel economy, and visa versa.
Often times, there may be 6 or 8 different props
that seem to run about the same, with differences
so subtle that any of them could be considered
satisfactory by most standards. This just makes
it that much harder to make a decision and choose
the right prop.
The purpose of this article is not to explain
propeller theory or hydrodynamics, but rather
to point out the various options in the market
place and set some common rules of thumb. It will
confine itself to the discussion of 3 and 4 blade
stainless steels props as these are the most common
in the real world.
Three Blades or Four?
In general, 3- blade props are the most common.
They are available in wide size ranges and cost
less than 4-blades. They typically yield a slightly
higher top end speed than 4-blades. They are available
in a wider variety of designs and offer more left
hand rotation pitch options for twin counter-rotating
Four-blades have some features of their own,
though. They often provide more lift at the stern
which will help accelerate the hull, especially
if it is stern heavy. They come out of the hole
strong and work well for pulling skiers and water
toys. In fishing and offshore boats, they are
oftentimes slightly faster than 3-blades at mid-range
rpm’s, where coastal anglers most often run their
engines. They also deliver slightly better fuel
economy at mid-range rpm. Oftentimes, a poor-handling
boat will improve by switching to a 4-blade propeller,
and more often than not, a 4-blade will run smoother
with better balance than the 3-blade equivalent.
A 4-blade propeller will usually have a smaller
diameter for the same pitch size of the 3-blade
equivalent. This is one reason they spin up quickly
and yield good acceleration. The blades are often
a bit smaller but offer more total blade area
because of the additional blade, so they have
more grip on the water. When switching from a
3-blade prop to a 4-blade, you’ll usually need
to decrease the pitch by 1 or 2 inches to keep
the engine RPM in the same range.
Propellers are sized and described by their
diameter and pitch. A propeller listed as a 15 x 17 x 3 would indicate a 17 inch pitch, 3 blade
propeller having a diameter of 15 inches. Pitch
is the theoretical distance that the boat will
move forward with each revolution of the prop
shaft, minus the slippage. The pitch ultimately
is responsible for the top speed of the boat,
much like the main jet in a carburetor is responsible
for the ultimate power and speed of an engine.
The pitch must be matched to the engine’s recommended
rpm range for full throttle. For most engines,
this top range is about 500 to1000 rpm (typically
5,000-5,500 for 2-strokes, 5,000-6,000 for 4-strokes).
A light boat and load will pull a high numerical
pitch prop, whereas a heavy boat and load would
have to run a smaller numerical pitch to load
the engine less and allow the engine to reach
recommended full throttle rpm. Keep in mind that
most propeller manufacturers design their pitch
in a progressive manner, to the point that the
actual pitch will vary across the blade surface.
Also, keep in mind that different propeller manufacturers
each measure their pitch in slightly different
ways with different tolerances. This means that
two propellers of the same diameter and pitch
from two different companies can yield different
For anglers slow-trolling for species like rockfish
and flounder, a propeller with lower pitch (less
distance per turn) that still allows the engine
to rev to the top of its range will offer lower
trolling speeds. It will also push loads easier
and make maneuvering around a dock easier. On
the other hand, a prop with more pitch that lets
the engine turn to the lower end of its range
may yield higher top speed.
Hooking-Up with the Water
There are other dynamics that come into play
as the boat accelerates to its top speed. When
it’s sitting still in the water and the skipper
advances the throttle(s), the diameter and surface
area of the prop develop the initial static thrust
and launch the boat. As the hull gains momentum
and speed, the dynamic thrust now is largely influenced
by the prop’s ability to connect itself to the
water and hook-up without cavitating or ventilating.
Cavitation is loss of hook-up due to the water
literally boiling, caused by extreme low pressure
near or at the blade surface or blade edge. Ventilation
is a loss of hook-up due to the introduction of
air or exhaust gases around the propeller. Basic
blade design and diameter can affect these problems.
If the diameter is too small for instance, it
can cause cavitation. If the engine is mounted
too high, it can cause ventilation. Both of these
phenomena can be minimized by installing the correct
prop. Going to a larger diameter or switching
to a 4-blade can sometimes accomplish better hook-up.
Larger diameter propellers usually yield better
maneuverability as they push a larger volume of
water on initial rotation, especially at slow
speed. They also grab more water for better control
when reversing. Matching the diameter and pitch
for a given load and application gives the best
performance for a specific boat.
Another design concept, called cupping, can
also come into play here. Cupping means curling
the trailing edge of the blade slightly to better
grab water as it comes off of the blade face.
This facilitates hook-up, but it can also load
the engine more, much as adding pitch does. Different
series of props have different amounts of cup
in them. It is not uncommon today to have props
with cupping added to the tip area of the blade
to minimize tip losses and maximize efficiency.
Vented props are available with an exhaust relief
hole at the base of each blade. These holes can
range from ? inch to approximately 3/8 inches
in diameter. They allow exhaust gases to escape
around the propeller as it begins to spin up on
acceleration. The engine gains rpm more quickly
and reaches its ideal power curve sooner to improve
overall acceleration. These props, however, do
not work well for fishermen who do a lot of slow
trolling, as the boat never gains enough speed
to leave the ventilated water, causing the prop
to catch-and-release, making the boat surge. Vented
props also do not work well with cat hulls.
Matching style, blade design, pitch, and diameter
is just as important for boat handling and safety
as for maximizing cruising speed and fuel efficiencies.
Large diameter props with lots of surface area
help a boat climb a big wave and allow the operator
to maintain good control in offshore conditions
with rough water. Again, good-hook up is essential
without overloading the engine and prop to the
point of causing cavitation.
If you can find a prop that seems to feel good
and run with confidence, don’t be discouraged
if it’s off by a little bit in ideal engine rpm.
Any competent prop shop can fine-tune and tweak
a good prop to make it perfect for your application.
Adding or removing pitch up to 1 inch is not uncommon.
Adding or removing cupping is also a standard
adjustment. It is nearly impossible to find the
right prop without going through a dedicated session
of trial and error. With so many styles, designs
and options in the market today, there is much
to be gained by simply trying as many props as
you can. It is important to do any comparative
analysis between props in the exact same water
conditions as each other, so that you can actually
come away with usable data.
Each of us has unique desires and requirements
for our propeller choices. They should always
be matched to a particular hull, load and usage.
My personal desire is to find a prop that I consider
to be well balanced. By that, I mean one that
handles well, yields average mid-range and top
speeds, with no quirkiness or negative traits.
I am always willing to sacrifice top speed to
achieve good all-round performance, as I run wide
open no more than 10% of the time, due to water
conditions, comfort level and passenger security.