Boaters anticipating the reopening of Fire Island’s Watch Hill marina later this summer will have to wait a bit longer.

A $5.4 million project to repair damage inflicted by superstorm Sandy in 2012 now will cost an additional $1.5 million and not be finished until the end of the year, the National Park Service announced Thursday.

Work on the project began in September 2016. Besides the 50-year-old marina, the visitors center, bathrooms, beach and tent campground remain closed.

“With more time, unforeseen and necessary repairs to the substructure can be made so boaters and visitors can safely enjoy Watch Hill in the future,” Fire Island National Seashore facility manager Jim Dunphy said in a statement.

Watch Hill, which has 182 boat slips, lies across the Great South Bay from Patchogue.

A smaller national seashore marina, Sailors Haven, reopened in summer 2015 after months of Sandy-related repairs. That marina is located west of Watch Hill, across from West Sayville.

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“The Watch Hill marina project was engineered to ensure the marina is safe and can withstand storms for years to come,” Dunphy said.

The new Watch Hill plan includes “supplementing girders and backfilling some areas of the bulkhead,” he said.

As part of the initial repairs, an elevated electrical building was built, and conduit and conductors replaced, he said.

Once the substructure is shored up, wooden decking and new pedestals will be installed on the marina boardwalk.

The visitors center and a nature trail also are being renovated, officials said.

Watch Hill is expected to reopen for the 2018 season.