The Steam Packet says nine of its sailings are at risk of disruption this weekend thanks to Storm Amy.
Strong gales are expected across the island and British Isles throughout Saturday and Sunday.
The first affected sailing is the Friday 8am sailing from the island to Heysham, which will now leave at 7:30am, with passengers asked to check in by 7am.
The 1:45pm return sailing from Heysham to Douglas on Friday, which will now leave at 1pm. Passengers are asked to check in no later than 12:15pm.
However, this sailing is subject to possible disruption or cancellation and a final decision will be made by 8am.
The 7:41pm sailing to Heysham is listed as subject to probably disruption and a decision will be made by 5pm on Friday evening.
Liverpool
The 3pm Manannan sailing will now leave the island at 7am, with passengers asked to check in from 5am and no later than 6:15am.
That return sailing, due to leave Liverpool at 7:15pm will return from Merseyside at 11:30am, with passengers asked to check in by 10:45am.
Saturday
The overnight boat back from Heysham to Douglas, due to leave at 1:45am is also subject to likely disruption, with a final decision due by 5pm on Friday evening.
That disruption will continue on Saturday morning with a final decision on the 8am sailing to Heysham and its return being taken by 6am that morning.
A decision will also be taken on the 10am Liverpool sailing and its return by 7am.
The Steam Packet will also make a decision on the Saturday into Sunday Heysham sailings by 5pm on Saturday evening.
The company said: “Passengers may amend their bookings free of charge through their online account, or alternatively you can contact our reservations team on 01624 661 661 or 08722 992 992.”