The Steam Packet has drawn up revised schedules for the Manannan.
Last week the ferry company announced that the fast craft would operate on reduced power after suffering a mechanical issue with one of her four engines.
Operating on reduced power will add about 20 minutes to each journey.
The Steam Packet says it has been monitoring the impact on services over the last few days and, despite the deployment of additional resources at the ports, running on reduced power has impacted on departure times for sailings later in the day.
The Packet says it is revising schedules ‘in order to reduce inconvenience and allow passengers to plan their journeys’.
From July 17 to August 13, the originally-scheduled 3pm sailing from Douglas to Liverpool will now leave at the new time of 3.45pm.
The originally scheduled 7.15pm sailing from Liverpool to Douglas will now depart at the new time of 8pm.
In addition, the Steam Packet is asking foot passengers planning to travel on Manannan’s 7am sailings to Belfast or Dublin and 7.30am sailing to Liverpool to check in no later than 40 minutes before departure.
Early arrival will assist crew to ensure the vessel leaves as early as possible in order to preserve, as much as possible, originally scheduled arrival times.
The Steam Packet says it is making every effort to contact passengers affected by the changes.
It says it is vital that up-to-date contact details are given, both email and mobile telephone numbers, when bookings are made to ensure passengers can be contacted with any details of important changes to the schedules.
The Manannan engine issue is still being investigated, but is believed to be connected to a failed crankshaft. Repairs are provisionally planned for mid-September. Passengers affected will be contacted once a date is confirmed.