Passengers travelling by sea today will be using the Manannan and not the Ben-my-Chree.
It’s so extra freight can be brought over in the run up to Christmas.
The sailings will still depart at the same scheduled times.
Steam Packet Company Chief Executive Mark Woodward says: "I very much hope that passengers will understand the changes we have had to make to our timetable but this is necessary to ensure we can deliver the service that is expected by all of our customers at this critical time of year.
"As I have said previously poor weather over the last several days has compounded the problems and these changes will allow us to deliver the services needed in the run-up to Christmas to ensure goods are in the shops and where they need to be.
"Passengers on the affected sailings will be contacted by our Reservations Team.
"We will also keep passengers advised if any further changes are required."