a propeller having a hub with a shaft hole at the center thereof , and a number of blades provided radially around the hub ; a shaft connected at one end to a motor driving the marine vehicle , the shaft being adapted to the shaft hole , and having a threaded portion arranged at least partially in the longitudinal direction thereof ; at least one bearing provided on the shaft for bearing the propeller to the shaft , the at least one bearing being rotatable in a single direction ; a connection hub associated with the hub of the propeller , the connection hub comprising a threaded portion being screwable to the threaded portion of the shaft in the direction opposite to the rotatable direction of the at least one bearing , and being non - screwable to the threaded portion of the shaft in the rotatable direction of the at least one bearing .