The Steam Packet Company says the Ben my Chree won't return to the Island until the end of this month.
The announcement comes after scheduled maintenance found stern tube bearings need specialist repairs.
The company says the Manannan will provide daytime passenger services, with the MV Arrow continuing its overnight freight services.
Its reservations team will contact any passengers affected by the delay.
Coastguards and firefighters rescue boy from cliff
12-seater ferry to Cumbria coming soon?
Lifeboat launched to help fishing boat
Smartmeter alert problem now fixed, says Manx Utilities
Merchant Navy Day marked this week
Filipino festival planned for Laxey
Glen Maye requisition meeting scheduled