CHICAGO (CBS) — Ask any Chicago-bred baby boomer to name a freighter that traversed the Chicago River in the past 50 years, and you will probably be told, “the Medusa Challenger.”

WBBM Newsradio has learned exclusively that time may be running out on the venerable cement hauler.

Back in the day, between 1968 and 1979, the ship was infamous for tying up downtown traffic. She was so long that three bridges at minimum had to be raised at once, and the fit was so tight that her passage often left bridges out of joint on her trips between Charlevoix, Mich., and Goose Island.

Problems were so frequent that the Chicago Tribune once published an article when no bridge leafs became stuck.

At 552 feet in length, the ship known today as the St. Marys Challenger remains the longest and largest ever to navigate the Chicago River. Since 1979, she has berthed at Lake Calumet, making the three-day round trip at a speed of 10.5 knots 70 or more times a year.

The Challenger wears another badge of distinction — at 107 years, she is the oldest U.S. flag merchant vessel in active service. Enthusiasts — and the ship has many of them — say the next oldest merchant ship on the Great Lakes is 36 years younger. But in weeks, the Challenger could be sliced down to a barge.

She is due for a five-year federal inspection, and owner Port Cities Steamship Services President Chuck Canestraight said at the very least she needs to be re-engined. He said the aging Skinner Marine Unaflow steam engine, which burns bunker oil, is no longer cost effective to maintain. Two nearly identical engines power the car ferry S.S. Badger, and Canestraight said the federal government has mandated that all such engines be replaced no later than 2025.

The final straw could be related to the engine, although Canestraight said it continues to run well. Canestraight said that over the past century, the vast majority of the ship’s steel plating and superstructure has been replaced with one exception — the plating and steel in the engine room area. He said if the inspection turns up no sizable problems with the engine room-area steel, at the rear of the ship, the cost of installing a modern diesel engine and cutting down the ship to a barge become virtually equal, in the $15-20 million range. But he said any mandate to replace that steel makes the decision easy — and one that preservationists won’t like.

“If the authorities were to say restore that entire hull under that stern and re-power it, we’d certainly be looking at a conversion to a notched, unmanned barge,” he said.

Canestraight said maintaining any piece of machinery that old can be interesting, and calls some of the repairs that have been made to the St. Marys Challenger “near misses.”

“On a year-to-year operating basis, I will say that it’s always interesting to have some old DC electric converter or some switch generated in the ’30s or what-not go bad on you and then hand it over to some contractor as you smile and look for a solution,” he said.

The ship was threatened with conversion to a barge once before, but the nosedive in the economy in 2008 postponed any change.

Those who have ridden aboard the Challenger — it has several forward passenger cabins — say it is a study in contrasts, with a modern satellite navigation and weather radar units sitting inches from a hand-crank phone linking the wheelhouse with the captain’s quarters. The phone system still works.

The Challenger is expected to make three more round trips before heading to dry dock at Bay Shipbuilding Co., in Sturgeon Bay, Wis., and the way Canestraight speaks makes preservationists take pause.

“If anyone wants to be assured to see her in her original shape as a 1906-built steamship, they ought do that” during one of this fall’s remaining trips, he said.

The Challenger would retain value as a barge for its main customer, St. Marys Cement Co., because of its size. Although small by today’s Great Lakes freighter standards, Canestraight said it transports an amount of powdered cement equal to what silos at Lake Calumet’s South Chicago Terminal can hold at any given time.

Port Cities has already transformed another veteran cement hauler from ship to barge. The Challenger has a crew of 25, but a tug would have half the crew.

Fans of the ship have set up a Facebook page in recent days in an attempt to build support for its preservation, and have told WBBM a re-engined Challenger would suit them fine.

“It doesn’t look good at all,” one backer wrote WBBM.

The fan noted that the Challenger weathered a killer storm in 1913 in which 19 ships sank and 250 people died.

“This historic ship deserves a better fate than being a barge,” he wrote.

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