A nacelle-mountable lift system for mounting and dismounting a rotor blade of a wind turbine involves a jib crane, the jib crane having a base removably mountable on a nacelle of the wind turbine and a jib mounted on the base. The jib has a boom arm supported on the base by at least one support strut extending between the base and the boom arm. A winch is mounted on the boom arm. At least two sheaves are rotatably mounted on the boom arm. A holder is connectable to the blade. At least two lift cables pass over the at least two sheaves connecting the holder to the winch. The boom arm is positionable to position the holder beyond a rotor hub of the wind turbine when the crane is mounted on the nacelle.