When boarding an outward bound ship or vessel at the boarding stations bar pilots shall remain on board the ship until she crosses the bar, unless permission is given by the master for the pilot to absent himself from the ship or vessel.  If the sailing of the ship is delayed for more than two hours by the master or owner after the pilot has boarded the ship and the pilot has not been given permission to leave, then in addition to the regular charges provided in this Sub-part, the pilot shall be paid for detention at the rate of five dollars for the first two hours and two dollars per hour or fraction thereof thereafter, until the ship or vessel sails.