|
Discount Inboard Marine (DIM) Featured Product
 |
Acme
#540
13" x 12 pitch 3-blade NiBrAl, (Nickel, Bronze, Aluminum)
1" Right-hand Rotation |
|
All
I can say is WOW!
By Keith Bagley, CorrectCraftFan.com
June 2004
 Prop
technology sure has come a long way in the last two decades! This past weekend,
I tested the Acme #540 3-blade prop and was blown away by
the improved performance to my 1979 Correct Craft Mustang. It was like I added
30+ horsepower to my stock PCM Ford 302 4V – hole shot, tracking, wake size
and low RPM speed control were all drastically improved – while actually adding
to the top-end!
From the moment I took the 540 out of the box, the differences between it
and my original 1979 12" x 14 pitch Federal Propeller (i.e. Michigan Wheel)
were glaringly evident. The visible surface area of the 540 dwarfed my old
prop. Looking straight on to the 540, it's almost as if the leading edge of
one blade overlaps the trailing edge of the next. With all this extra surface
area you might think there would be more drag and a loss of top-end speed.
Not the case with the 540. With roughly 500 lbs. of people and gear, the top-end
speed actually increased 1.1 m.p.h.. With that same amount of weight, the
0-30 m.p.h. time improved by over 1.5 seconds.
Acme 540 3-blade compared to original 1979 Federal Propeller 3-blade:
|
|
1979
Federal Propeller |
Acme
#540 |
| 0-30
m.p.h. |
8.92 sec. |
7.22
sec. |
| Top-end
speed |
44.1
m.p.h. |
45.2
m.p.h. |
Test conducted under
identical conditions with roughly 500 lbs. of people and gear in boat using
handheld GPS unit to measure m.p.h. and a separate handheld stopwatch to measure
elapsed time. Boat used was a 17' 1979 Correct Craft Mustang with stock PCM
Ford 302 4V listed at 220 hp. Boat weight listed at 2000 lbs.
Another noticeable difference with the 540 was the increased power throughout
the full range of RPMs. Acceleration was drastically better from 0-30 m.p.h.
but was equally impressive from 10-20 m.p.h., 20-30 m.p.h., and 30-40 m.p.h..
The 540 increased power so
| If there
is only one improvement you can make to your older Correct Craft, get
an updated prop. |
much that it actually affected
the boat's position in the water – raising the stern, creating better front-end
tracking while decreasing
wake height at various slalom speeds. Likewise, there was a tremendous improvement
in speed retention at lower RPMs.
According to Bill Weeks, Sales Engineer at Acme Marine Group, "I recommend
the Acme 540 13x12 3-blade Nibral 1" bore for skiing and the 542 13x11.5 3-blade
Nibral 1" bore .080 cup for wakeboarding with the direct drive [1:1] ski boats.
We do make a 4-blade but the Acme 3-blade will out perform the 4-blade in
every way."
Beyond the increased performance, there was a noticeable decrease in prop
vibration and hull noise. Typically with my old prop, I would tolerate a certain
amount of vibration and accompanying hull noise as I pushed beyond 3,000 RPMs.
With the 540 there was no vibration and virtually no noise.
Replacing
12" Props
On the older non-Nautique Correct Crafts (like my Mustang) that
came fitted with a 12" prop, you can move up to a 13" prop.
Woody from Southeast Correct Craft recommends there be a minimum
distance between the prop blade and the hull equal to the shaft
diameter or there can be damage to the hull gelcoat over time. After
you have installed your new prop, measure at a 90 degree angle from
the shaft at the point where the blade is closest to the hull. If
the distance is less than one inch and you notice extra
vibration or at the first signs of marking on the hull right above
the blade, you can send your 13" prop back to Acme and they
will trim a little off each blade so that it fits you boat properly. |
|
Apparently this has to do
with design and precision CNC machining that was unachievable 25, 10, or even
5 years ago. According to Acme, it is this accuracy that makes their 3-blade
props incredibly smooth while increasing surface area equal to that of the Acme
4-blade. The result is remarkably improved hole shot and an increased top-end,
all while holding power and control throughout.
Word of caution: This increased surface area has a radical affect on 'breaking'.
The first time I pulled back on the throttle it was as if I had jammed on
the breaks in my car. The 540 grips the water like a tire on pavement while
on or off the throttle.
If there is only one improvement you can make to your older Correct Craft,
get an updated prop. After all, despite all that horsepower, the prop is were
the rubber hits the road (so to speak). The technology in today's inboard
specific props can have amazing results on your older Correct Craft. Do yourself
a favor and upgrade that 10, 20 or 30 year-old prop. Trust me, it will breathe
new life into your older boat and you will be thanking yourself for years
to come.
Views expressed in this analysis are solely those of CorrectCraftFan.com and not those of Correct Craft, Inc.
Discuss this Article
 The
full
line of Acme props are available from Discount Inboard Marine. For more
information visit http://www.SKIDIM.com
or call 803-345-0996. When ordering, be sure to
enter the promocode CCFAN to receive 10% off.
|
