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| Outboard
Questions • Sterndrive
Questions |
Q:
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Should
I use 2-, 3-, 4-, or 5-blade propellers?
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A: |
Excessive horsepower, direct drive and high advanced speeds
indicate that propellers of high pitch-diameter ratio be employed.
Generally 2-blade propellers are used. At somewhat lower advanced
speeds and shaft speeds, 3-blade propellers with pitch-diameter ratios
of approximately 1.0 are required for best properly efficiency. It
is in the category that most pleasure boats lie. At even lower advanced
speeds and shaft speeds, 4-blade propellers with pitch-diameter ratios
of approximately 0.8 or less are required for optimum propeller efficiency.
On large cruisers and commercial applications such as trawlers, shrimpers,
tugs and workboats, 4-blade propellers are generally used. If excessive
vibration is a problem, 5-blade propellers are used. |
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