To improve an outboard motor propeller for a motorboat racing boat and more specifically to improve an outboard motor propeller for a motorboat racing boat used for a racing boat outboard motor used in a motorboat race.

Damage of a wing by a tool such as a plier and breaking of a wind end prevented at attachment/detachment of the propeller by changing a position of a fitting groove of a shear pin positioned at a boss front end of the propeller to a position deviated from the present X-X line to a rotation direction by a required angle and the wing can be formed on a portion where the wing cannot be formed conventionally. Thereby, the problem wherein (1) at attachment/detachment of the propeller 10, flaw on the wing or breaking of the wing end by the tool such as the plier is frequently generated in a work for removing a split pin; (2) when the flaw on the wing surface of the propeller or breaking of the wing end is generated, the fact becomes a cause for causing reduction of performance and reduction of durability of the propeller; and (3) even slight reduction of performance and reduction of durability of the propeller, trouble is brought about at navigation, the extremely dangerous state is optionally caused and occurrence of an accident resulting in injury or death caused by this is also anxious is solved.