The dry dock has been good to the John G. Munson. Since her launch in 1952 at Manitowoc, Wis., as a member of the Bradley Transportation Co. fleet, she has been up on blocks every few years for a scheduled variety of major repairs, overhauls, rebuilds and productivity and safety improvements.

She started her service on the Great Lakes at 666 feet with coal-fired boilers, and today she still has a beam of 72 feet and a depth of 36 feet, but she’s 102 feet longer and is powered by oil and is more maneuverable than she was at her launch now that she’s equipped with bow and stern thrusters. She’s even a different color, having been made over, in 1990, from the gray of the Bradley fleet to the red of the Great Lakes Fleet.

In this rarely seen view of the inner workings of the Munson’s rudder, a plate has been removed for access to the shaft that serves as the rudder’s pivot point. The shaft has been removed, too, for inspection.

And this winter she has been back in Superior’s Fraser Shipyards for yet another round of inspections and major work. It’s all part of a carefully scheduled maintenance program that the American Bureau of Shipping, the Coast Guard and all Great Lakes carriers adhere to. And, although the Munson has been this winter’s only vessel in the Fraser dry dock (or, more accurately, its graving dock), it is just one of 11 vessels in the Twin Ports over the 2006-07 winter layup. All of them will undergo maintenance and repair.

The Port’s facilities manager, Jim Sharrow, estimates that the vessels’ owners will pour $500,000 to $800,000 into each laker during layup. “All our operators have been very busy, and they need their vessels to be dependable,” Mr. Sharrow said.

The Munson, though, stands out this season with repairs that Don Lindquist, Keystone Shipping Company’s fleet engineer, pegs at at least $2.5 million. Here’s just a sampling of the work that Mr. Lindquist is overseeing while the Munson is at rest:

Hull inspection. (“It’s in excellent shape,” Mr. Lindquist said.)

Hull painting, including remediating the last of the boat’s lead paint, which was on the bow. (Painting goes like this: after sand blasting and scraping are complete, a black epoxy goes on the hull; that is followed by a red oxide first coat; that is followed by a red oxide urethane coat, which gives the boat its distinctive glossy finish.)

Brick work in the boilers.

Propeller blades, hub and tailshaft inspections.

Bow and stern thruster inspection and overhaul.

Replacing approximately 50,000 pounds of steel in the cargo holds to replace materials that were showing the inevitable signs of wear and tear.

A “tremendous amount of work on the bucket system” — with at least 60 of the vessel’s 71 buckets being repaired or replaced and all the upper rails on which the buckets ride being replaced. These buckets are the heart of the ship’s self-unloading system; it’s the buckets that lift taconite pellets, crushed limestone or coal out of the vessel’s seven cargo holds and deliver the product to the boom, which in turns deposits the product on shore.

Attention also is being paid to the ship’s other heavy components in addition to motors and valves and pumps and switches and all the other parts and pieces that have to run in synch in this huge ship — most of them well concealed from the admiring eyes of Great Lakes boatwatchers — that make this vessel and others like it a hard-working floating marvel of engineering efficiency and durability. With her capacity of 25,550 tons, the Munson moved nearly 2 million tons of cargo last season over 90 visits.

The Munson’s propeller — four 5,800-pound blades — was disassembled and carefully inspected. (The prop on your 25-horse outboard should look so good.)

When we say ‘on the blocks,’ we mean on the blocks.

The Munson, a self-loader with its forward-mounted boom and thrusters, has long had a well-deserved reputation for productivity and dependability, Mr. Sharrow said. “It’s one of our most productive boats,” he said. “Because it’s so flexible around the docks, the Munson is requested by a lot of dock owners.”

The Munson’s 2007 order book might be filling up fast, but her customers will have to wait just a bit longer. Work that started three days after her January 7th arrival at Fraser Shipyards will continue till she’s scheduled to sail again on or about March 23rd.

But in the meantime a crew surge of about 40 workers is expected to be on board for two to three weeks to install those 50,000 pounds of new steel to protect the cargo holds. Also, the four 5,800-pound propeller blades — made of nickel, aluminum and bronze — have to be reinstalled, the bucket system has to be reassembled and installed, painting needs to be completed, shore services personnel still have to wrap up their lighter work, final inspections have to be completed and a crew needs to return from Rogers City, Mich., to fire the boilers and get this ship underway and back to work.

With all that done, the Munson will be back in the water where she belongs. And in five or six years, she’ll be back in dry dock, and we’ll do it all over again.