The Steamship Authority’s M/V Nantucket was back out of service on Wednesday and Thursday due to a nagging mechanical problem that first arose last weekend, leaving some cars and passengers stranded on both the Island and in Woods Hole.

On Saturday morning, a governor, an engine device that regulates speed, failed on the Nantucket, taking the boat out of service until the following day. But a Coast Guard inspection found the governor needed additional repairs, meaning the boat was back out of service by Wednesday, SSA spokesman Sean Driscoll said.

“There wasn’t a new problem, it’s the same governor, the Coast Guard just wanted some additional repair work done,” Mr. Driscoll said.

The vessel missed its 11:05 a.m. departure out of Woods Hole and its 12:20 p.m. return from Oak Bluffs. Mr. Driscoll said he was unsure how long the repair will take.

“We don’t know at this point how long the Nantucket’s going to be out; we’re hoping that repairs will be done today,” Mr. Driscoll said.

The M/V Sankaty will run in place of the Nantucket starting with the 1:35 p.m. boat, Mr. Driscoll said. The Sankaty carries up to 300 passengers and crew compared to the 768-person capacity of the Nantucket.

“We’ll accommodate the vehicles that can’t fit on the Sankaty with a different trip,” Mr. Driscoll said. “And then we’ll take it as it comes throughout the rest of the evening.”