Every person holding an appointive office or employment in the city government on the effective date of this charter shall retain the same or the similar office or employment hereunder, pending action by the competent authority of the city having the power of appointment and removal with respect to such office or position. At any time within four months after the effective date of this charter, the city manager and the general manager of the water department in office on that date shall be subject to replacement by the council and by the water board, respectively, without regard to the removal provisions of sections seven and twenty-eight of this charter.