The Canadian Coast Guard and a Hamilton shipyard are reviewing whether taxpayers will pay the full $4-million contract for a much delayed refit of an oceanographic research ship.

The CCGS Hudson was towed out of Heddle Marine on Oct. 6, months behind schedule and the refit work not completed. The ship was supposed to be ready in May.

The coast guard is refusing to say what delayed the maintenance work, which included overhauling the superstructure and masts, blasting and recoating the hull, along with steel replacement and repairs to the rudder.

"The refit work for the CCGS Hudson took longer than originally planned," coast guard spokesperson Vance Chow said in an email, adding the federal government "is working to resolve issues and bring the vessel back in service as soon as possible."

CCGS Hudson in Bermuda in 2016 during a mission to research deep ocean areas. (Submitted by the Department of Fisheries and Oceans)

He said Public Service and Procurement Canada and Heddle Marine "are currently reviewing contractual requirements to determine if any change to the value of the contract will be required."

The coast guard is minimizing the extent of work remaining on the 54-year-old vessel. It said the company completed dry-dock work the day before the vessel was towed to a nearby federal facility to complete required maintenance.

"There is a minor quantity of known work that was not completed prior to the work period end date, including some paint work and cleaning," Chow said.

"This work is currently being undertaken in conjunction with preparations to return the vessel to service."

The 54-year-old Hudson was supposed to be ready to go back in service in May. (CBC)

With the Hudson unavailable, the coast guard and Department of Fisheries and Oceans have scrambled to find alternative vessels to carry out scientific cruises.

In some cases, other coast guard vessels have been pressed into service. Where they are unavailable, the government is also seeking private charters.

The most recent request closed on Oct. 10 for a vessel to carry out an ocean condition survey off Nova Scotia in November.

It is normally conducted in September.