Abstract: A propeller assembly is provided for mounting on a rotatable propeller shaft of a watercraft. The propeller assembly includes a hub structure having a plurality of circumferentially spaced blades projecting therefrom and an inner surface defining a passage. An adaptor is receivable in the passage of the hub structure. The adaptor a plurality of key pairs extending along the outer surface thereof the adaptor which define slots for receiving inserts therein. An inner portion of the first side of each insert forms mating relationship with first portion of the first sidewall of a first key of a corresponding key pair and an inner portion of the second side of the insert forms a mating relationship with the first portion of the second sidewall of a second key of the corresponding key pair with the insert received in the corresponding slot.