The Peel Harbour swingbridge will be closed to pedestrians for three days while work is carried out.
There will also be no access to the inner harbour for boats from Thursday to Saturday in the high water period.
The work is a scheduled hydraulic oil change, which usually takes place later in the year, but has been brought forward by the Manx government.
Dredging work is ongoing and has been delayed because of bad weather. It will now continue until the end of April.