The ferry, the first of a fleet of six such craft, was due to be pressed into service this month on the inner harbour, from Watsons Bay in the east to Cockatoo Island in the west, but sources say the retrofit work needed to bring it up to scratch means it is unlikely to be launched until March.

While it is not uncommon for new vessels to need alterations before they launch regular services, the raft of design issues found on the Catherine Hamlin is said to be significantly larger than usual.

The major problem encountered since the catamaran ferry began trials on Sydney Harbour in November has been maneuvering the vessel in high winds due to its shallow hull and small rudders, which has led to it sliding sideways on occasions.

"These problems will be rectified but ... it is just going to take time to fix," a source said.

The ferry is likely to need to be placed in a dry dock to allow its rudders to be replaced or altered to give it greater stability in the water.

The vessel, named after a pioneer in Australian medicine, is the first of six new ferries built by Tasmanian shipbuilder Incat, which is due to deliver all of them to the NSW government by the end of the year as part of an upgrade of Sydney's fleet.

Transport for NSW said it was "working with our designers and operators to make some adjustments to ensure that we maximise the performance" of the Catherine Hamlin following a number of trials since its arrival in Sydney.

"In the meantime, preparations are continuing for her entry into service, including crew training," a spokesman said.

He declined to outline what adjustments would be made to the ferry or when it would begin regular passenger services.

The changes to the Catherine Hamlin will be incorporated into the other ferries before they are completed at Incat's Hobart shipyard.

The new catamaran ferries will each carry up to 400 passengers and be run by the city's main private operator, Sydney Harbour Ferries. It recently extended a contract by another year to charter four vessels from Captain Cook Cruises operator Sealink.

The O'Farrell government awarded the Sydney Harbour Ferries consortium an $871 million contract in 2012 to operate the state's ferries for seven years.

The Catherine Hamlin and the five other 35-metre vessels to be built in Tasmania will replace some of the First Fleet ferries, which have sailed the harbour for decades.

They will be the first new vessels in the government-owned fleet since 2000 and 2001, when four SuperCats entered service.

Meanwhile, the completion of two new ferry wharves at Barangaroo, on the western edge of the central city, is running several months late.

The "ferry hub" was slated to be opened late last year but is not expected to begin handling passengers until March.

Incat declined to comment on the Catherine Hamlin or the work on the other ferries it is building for the NSW government.