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"Is
a 4-Blade Prop Better than a 3-Blade?"
| It depends! There's nothing magic about either a 3 or
4 (or more) blade propeller. The best number of blades for your
application depends on a multitude of factors such as boat weight,
distribution of weight, power, reduction gear, clearance, bottom
configuration etc.. There is a good chance (but not a certainty)
that the manufacturer that built your boat or the Naval Architect that
designed it gave some thought to these factors and delivered your boat
with the right number of blades based on pre-delivery testing. On
the other hand, we have seen performance improvements achieved just from
decreasing or adding blades, so we do look at this question on a case by
case basis.
We'll be happy to consult with you on the number of blades issue, and
may even have experience that directly correlates to your
application. However, keep in mind that we may be covering ground
already trod by your boats' manufacturer in a "trial and
error" and testing phase.... A call to them may save effort on your
part.
That said, there are some generalities when comparing 3 & 4 blade
propellers that can be stated with a fair amount of certainty (assuming
that both the 3 or 4 blade propellers being compared are properly tuned
and are the proper size to allow engines to reach rated rpm"s).
 | A 4 blade propeller has more blade area than a 3. |
| This increased blade area will provide better maneuverability on the
low end. |
| A 4 blade propeller will generally handle weight variations
less noticeably than a 3. |
| A 4 blade propeller will generally come "out of the hole"
better. |
| A 4 blade will run harmonically quieter than a 3. |
| Because of the extra drag caused by the 4th blade, a 4 bladed propeller will be slower on
the top end than a 3. |
| A four blade propeller will have to be smaller in diameter, pitch, or
cup to achieve same rpm's as a 3 blade. |
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