The Isle of Man Steam Packet Company says the Ben-my-Chree is about to head off for its biennial checkup.
The vessel is due to head to Birkenhead from April 16 until May 5.
The company says a large capacity freighter has been chartered from Northlink Ferries, while the Manannan take over passenger and car services.
Chief Executive Mark Woodward says the dry-dock dates were confirmed in January this year and the replacement freighter will offer one return sailing each day from Heysham.