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Which propeller should I choose, the Acme 3-blade or the Acme 4-blade?
Theoretically, a 3-blade propeller should always be more efficient than
a 4-blade. However, in the past, two big issues have prevented the 3-blade
from taking the lead in popularity. The first was a lack of manufacturing
precision, which commonly caused 3-blades to vibrate more than 4-blades. When
significant dimensional variation exists in a propeller, vibration is generally
more noticeable in a propeller with fewer blades. The second reason for the
3-blade disfavor was an almost certain loss of blade area in the transition from
four blades to three. Consequently, even though top-end gains were achieved,
performance expectations on the low-end were diminished.
Through the implementation of precision manufacturing and design improvements,
Acme Propellers are giving the 3-blade the reputation it deserves. Acme is
consistently holding tolerances never before achieved in propeller production. This
accuracy makes the Acme 3-blade incredibly smooth. In addition, the blade area
of the Acme 3-blade has been expanded to equal that of the Acme 4-blade. The
translation? The Acme 3-blade has raised the performance bar. From an awesome
hole-shot to an unmatched top end, and all the smoothness throughout, the Acme
3-blade leaves nothing to be desired. We believe it has an edge that everyone
will appreciate. On the other hand, please do not mistake our excitement as
a lack of appreciation for the Acme 4-blade, a proven winner.
It should be noted that this choice might still be mildly influenced by
application, because it is possible that the most perceptive users might be
able to detect slight differences that cause them to prefer one prop over
the other. Even still, the overall performance of either Acme Propeller is
paramount, and is that from which dreams are made.
Can an Acme Propeller improve my performance?
Yes! Just ask any professional slalom skier or wakeboarder. Or ask any OEM
(boat builder) or Inboard boat dealer using Acme Props. The words we hear
most often are “unbelievable” and “awesome”. And if
an Acme Prop can make an old boat seem like new again, then it can certainly
improve the smoothness and performance of your boat. Nevertheless, there are
some very important things to be aware of when choosing an Acme Prop. As is
the case with any propeller, it is absolutely essential to choose the correct
size for your boat, engine and application. The size of your current prop can
be helpful in determining the correct size Acme Prop, but if you simply replace
your current prop with the same size Acme Prop, you may be disappointed. Acme
Propellers tend to be more efficient and usually run lower in pitch and/or
diameter, than hand-made or hand-finished props on the market. In addition,
Acme does not round off dimensions, as is common with other propellers (e.g.,
an Acme 12.5 x 15.5, Variable design, measures precisely 12.5” in dia. and
15.5” pitch at 0.5R). Furthermore, varying propeller characteristics can
lead to performance concerns due to the proximity of the propeller in relation
to the bottom of the hull or the leading edge of the rudder.
Also be aware that even though the propeller can make a huge difference
in boat performance, it is still only one determining factor. The engine,
transmission and hull, etc., must also be functioning properly in order to
achieve optimum performance. Fortunately, Acme has reduced the number of
variables by developing the “propeller constant”, to make your
job easier. If you have any questions or concerns in choosing the correct Acme
Propeller for your boat and application, please give us a call.
If I damage my Acme Propeller, how easy will it be to have it repaired?
No problem. Even though Acme Propellers have a unique look, there is
really no difference in the way they are repaired. As can be expected, it is
not possible to return an Acme Prop to perfectly new condition, because this
would require maintaining tolerances of plus or minus the thickness of a human
hair. However, in most cases it is easier to repair an Acme Prop, because of
the accuracy and consistency built into the propellers and the pitch blocks
from the start. Propeller blade thicknesses, for example, are consistent and
virtually identical to one another.
You may want to inform your repairperson that both Pesco Inc. (Ph. 800-835-6007)
and Rundquist Propeller Tools Inc. (Ph. 314-638-7667) produce pitch blocks for
the correct repair of Acme Props. Please be advised that some of the original
CNC tool lines, which are a product of the CNC manufacturing process, may be
altered or removed upon repair. The removal or buffing out of the machine lines,
in itself, does not hamper the performance of the propeller.
Keep in mind that the repair of any propeller, worth repairing, is only
as good as the shop that repairs it. Regarding Acme Inboard Wake & Ski
Boat propellers, if you are unable to find a good repair shop in your area,
give us a call for an RMA number and our repair ship-to address. We have
been repairing Acme Propellers for nearly a decade now and have encountered
absolutely no repairability issues. Furthermore, if your repairperson has any
questions or concerns about the correct repair of an Acme Propeller, ask them
to give us a call. We are happy to help.
Why are my maximum Engine RPMs important in choosing a propeller?
The maximum RPMs, or WOT RPMs (Wide Open Throttle), is an important benchmark,
most often used to determine the best size propeller for a particular boat and
application. If you think of your max RPM range as the target, your actual
RPMs as the arrow, and your propeller as the load, then simply put the load
can be adjusted to put the arrow inside the target.
Furthermore, by choosing a propeller with the correct combination of diameter,
pitch and cup, the max RPMs should be in the proper range to provide optimum
performance for the boat and engine at all levels of operation. Fitting your
boat with the wrong propeller can translate into a variety of problems (i.e.,
insufficient acceleration/speed/hold, over or under-revving, red-lining,
poor fuel economy, etc.).
Engine RPMs are affected by a variety of factors (i.e., the amount of
weight added to the boat, elevation above sea level, air/water temperature,
engine condition/performance, propeller size or condition, the condition or
attitude of the hull, etc.).
For typical applications the average user should have his or her max RPMs
in the target range for their engine under normal load conditions. Two common
applications that call for special propeller sizing are dedicated wakeboarding
or wakesurfing applications, that add considerable weight to increase the wake
size, and high elevation applications, in which the standard, stock propeller
can be too much load for the engine. If you have any questions about the
correct size Acme Prop for your boat,
please contact us.