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Selecting a propeller with enough blade area for the job
When air gets sucked into a propeller or when a partial vacuum forms around the blades, the effect is for the propeller to lose its grip on solid water and to race ineffectively.
Cavitation results when air is sucked into a propeller or when too much power causes bubbles of partial vacuum. The effect is for the propeller to race and lose its grip on the water.
Air can be sucked down when a boat makes a sharp turn or when wave action brings the propeller out of the water, but cavitation is also experienced when too much power is applied to too small a propeller, which then forms bubbles of partial vacuum.As water rushes in to fill the vacuum, it is vaporized. It implodes against the propeller with enough force to cause pitting. This, in turn, leads to poor balance, vibration, and further pitting, so that the metal of the blades is greatly weakened.

To prevent this permanent form of cavitation, the load on the propeller blades must be kept fairly low, which means increasing the size of the propeller or reducing the power of the
engine. A good safe level of loading for the propeller blades is about 6.4 pounds per square inch (450 g/cm2).If cavitation occurs with a two-bladed propeller, the answer is to change to a three-bladed prop with more area. If the culprit is a three-bladed prop, the answer is to increase diameter, select wider blades, or fit a four-bladed prop.See also Propeller Advances.
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