Two sailings of the Steam Packet vessel Viking will be taken by the company's other fastcraft - Snaefell - on Thursday, so a repaired gearbox can be refitted.
The company says it will be installed on Thursday evening so everything will be back to normal in time for the busy bank holiday weekend.
The affected sailings will be the 17.45 service to Liverpool, and the return crossing at 21.15 hours.
The 17.45 sailing will now go to Heesham, leaving Douglas an hour late, at 18.45, with the return service from Heesham to Douglas at 22.00 hours.
The damaged gearbox has added half an hour to all sailings by the Vikings for the past fortnight.
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