Steamship Authority officials are stumped as to how M/V Barnstable, the first of three recently-acquired freight ferries to enter service, suffered propeller damage so severe the vessel had to be taken out of the water last month for repairs.

“No reports were made from the vessel for this type of grounding,” SSA engineering and maintenance director Zachary Lawrence told the port council Tuesday, displaying photographs that showed bent and chipped blades on both of the Barnstable’s propellers, with the port side blades most heavily affected.

Chief operations officer Mark Amundsen said the damage was discovered during a routine inspection by divers checking the vessel’s bottom.

“We were very surprised. We were doing our annual dive survey [and] we had no idea of the damage,” he said.

Termporary replacement propellers were provided by the former owners.

Courtesy SSA

Termporary replacement propellers were provided by the former owners.

Courtesy SSA

Steamship Authority ferries on the Nantucket route often suffer propeller wear from the sandy bottom of Hyannis harbor, but Mr. Amundsen said the Barnstable’s prop damage appears to have been caused by something more resistant.

“The propeller blades hit some sort of hard object, rock or something similar,” he said.

In addition to the bent and nicked propeller blades, he said, the Barnstable also suffered damage to its hull.

“In the port forward quarter, we found some deep scraping … from port to starboard, athwartship [across the vessel],” Mr. Amundsen said, suggesting that the damage may have occurred while the ferry was turning. 

“We suspect that maybe when we were turning the vessel that that damage happened,” he said.

The Steamship Authority has inspected and found no similar damage to its other vessels on the Nantucket run, including the Barnstable’s sister ship M/V Aquinnah and the M/V Woods Hole, which Mr. Amundsen said sits lower in the water than the other two.

Continuing its investigation, he said, the boat line now is preparing to commission a subsurface survey using side scan sonar and a remotely operated underwater vehicle to look at a section of Hyannis harbor.

After its unscheduled dry docking to install eight new propellor blades — on loan from the vessel’s former owner, Hornbeck Offshore, until the Steamship Authority can obtain blades from the manufacturer — the Barnstable was back at the boat line’s Fairhaven maintenance facility Tuesday, preparing for its Coast Guard inspection before returning to service.

The SSA purchased the Barnstable and its sister ships, the Aquinnah and M/V Monomoy, from Hornbeck in 2022 and has spent millions converting them from offshore energy service vessels to freight ferries with room for 80 passengers.

Last of the three to undergo the process, the Monomoy remains quayside at Alabama Shipyard in Mobile, Ala., where Mr. Lawrence and Mr. Amundsen said its Coast Guard safety inspections are caught in a bottleneck caused by the federal shutdown.