The propeller with a small duct of the present invention has a propeller 10 attached to the stern of the hull 1 and a duct 20 attached in front of the propeller 10, and the diameter Ddin of the duct 20 is 20% or more and 50% or less of the diameter Dp of the propeller 10. The pitch H of the propeller 10 is a decreasing pitch that decreases in the radius R direction, which is the maximum value at the blade root of the propeller and the minimum value at the blade tip, and is characterized by both the large duct and the medium duct As an energy-saving device that combines features, the shape of the propeller 10 is devised, and the small duct 20 is placed close to the front of the propeller 10 to suppress cavitation in an actual sea area where the degree of load increases and to improve efficiency. The load distribution in the radius R direction of the propeller 10 to be controlled is optimized by utilizing the interference with the small duct 20.
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