PORTLAND – The Portland Fire Department should have reported an accident that damaged the City of Portland IV fireboat, and there are indications the vessel was outside a marked channel, Coast Guard officials said Thursday.

The fireboat hit something under water on the north side of Fort Gorges in Casco Bay shortly before sunset Saturday during what Fire Chief Fred LaMontagne described as a “navigation training” run.

The impact sheared off one of the boat’s two propeller shafts and damaged a propeller and the rudder. LaMontagne said he is investigating the accident, but comments by fire department officials to the Coast Guard suggest the boat may have been operating outside the channel when the accident occurred.

Lt. Nick Barrow, the Coast Guard’s sector command center chief, said he spoke with the department to determine where the accident occurred so that other vessels could be warned, if necessary. He said he was told the object didn’t pose a hazard to other vessels operating in the channel.

Asked if that suggested the fireboat was outside the channel, Barrow declined to comment. He said the Coast Guard was only concerned with whether to warn other vessels. LaMontagne also declined to comment, saying determining exactly where the accident occurred is part of his investigation.

The chief has also refused to say how many people were on the boat and who was at the helm.

Barrow and Lt. Mason Wilcox, chief of investigations for the Coast Guard in South Portland, said the accident should have been reported verbally Saturday night, and a written report was due within five days of the accident, which would have been Thursday.

Technically, hitting something that’s under water is considered an “unintentional grounding,” even if the vessel is able to continue on, as the City of Portland IV was able to do, Wilcox said. He also said the incident should have tripped other triggers for reporting, including an accident that limits a vessel’s maneuverability, or that is likely to cause more than $25,000 in damage.

LaMontagne said Wednesday that he didn’t think the city was required to report the accident, and Barrow agreed at the time. But Wilcox said Thursday the accident did meet the threshold for a report of a “marine casualty.”

It was the second time the $3.2 million fireboat has been damaged when it ran aground in Casco Bay.

In November 2009, the vessel hit a ledge in Whitehead Passage, the channel between Peaks and Cushing islands. The repair bill was $90,000, and the boat was out of commission for three months.

Saturday’s accident did not completely disable the boat, but it has been placed on limited duty, and the city’s older fireboat, the Cavallaro, will be used for most calls. The city plans to take the boat to a repair yard in Rockland as soon as weather permits.

The fireboat is insured under a policy that carries a $25,000 deductible.

Under Coast Guard regulations, the city could be fined up to $5,000 for a first offense of failing to report Saturday’s accident, but Barrow said that’s unlikely.

The Coast Guard has a great deal of latitude on whether to fine or warn over violations, Barrow said, and Portland is “one of our key port partners.” The Coast Guard is interested in maintaining a cooperative relationship for future joint training, island medical evacuations and bay search and rescue operations, he said.

Wilcox also said that the firefighters operating the boat – they’re called “pilots” by the Fire Department, because “captain” could be confused with a department ranks – don’t need to be licensed because the vessel isn’t commercial.

Some of the fireboat pilots carry Coast Guard licenses to operate vessels up to 100 tons gross tonnage, a figure that refers to a boat’s internal capacity or volume. But LaMontagne said the city allows unlicensed firefighters to operate the boat, provided they have trained under a licensed pilot.

He said the city considered requiring licenses for all fireboat operators a few years ago but decided not to because of the costs associated with getting a license and maintaining certification.

“We’re in challenging fiscal times and everything comes with a cost,” he said.

Wilcox said 100-ton licenses require time at sea, and hours spent on the fireboat or a private vessel would count. A written test also must be passed and captains are licensed for various types of waters.

LaMontagne said late Thursday that he and other fire officials plan to sit down with the Coast Guard in the next few days to review the accident.

Staff Writer Edward D. Murphy can be contacted at 791-6465 or at: emurphy@pressherald.com