O.J. Cenac, rated at 8,000 hp, is powered by three QSK60 engines from Cummins. The engines turn three 90-inch props enclosed in nozzles faired into the hull, giving the tug a 12-foot draft.
The 8,000-hp, triple-screw, red and white conventionally powered tugboat, named after the company founder, went to work in early June under the command of Cenac’s Capt. Joe Boudreaux.
Cenac’s newest vessel is also the first U.S. tugboat to make use of the new QSK60 marine engines, introduced in late 2002 as the most powerful marine engines in the Cummins inventory. With three of these new engines, each turning its own propeller, O.J. Cenac is rated as an 8,000-hp vessel, according to Walt Cenac, marine manager. The engines turn into Twin Disc marine gears with 7:1 ratios. The 90-inch props are enclosed in nozzles that have been faired into the hull to maintain the boat’s 12-foot working draft. The massive props are mounted on 9-inch shafts equipped with Kobelt shaft brakes to facilitate faster shifting of propeller direction.
Cenac, a well-known Gulf Coast operator of both inland and offshore towboats, has long had a preference for triple-screw propulsion for any of its vessels that handle oil barges.
“Right now we’ve got about 75 percent of our fleet operating with triple screws,” Walt Cenac said. “It’s mostly for reasons of redundancy and safety. We want to be always able to have our tugs maneuver as effectively as possible, and this way, even if they lose an engine, we’ll still have a fully functioning tugboat.”
O.J. Cenac also makes use of 90-inch nozzles around each of its propellers. Lately, the company has been fitting all of its offshore vessels with nozzles for the extra thrust. Many of its inshore boats go without nozzles, however, because of the greater possibility of debris jamming between propeller blade tips and the nozzle.
The last new vessel introduced by Cenac, in late 2000, was Andrea Cenac, a 100-foot, 2,550-hp, triple-screw vessel, also with Cummins power.
“The Andrea has been a very successful, strong-pulling boat, and that success has led to the design of this larger boat,” Cenac said. “Actually the design is a collaboration between Main Iron Works and Cenac Towing. We like a boat with classic lines but still with the latest equipment.”
Leroy Molaison, operator of Main Iron Works in Houma, La., explained that his shipyard did all the steelwork, and installed shafts, propellers and some of the piping before the hull was towed to the nearby Cenac dock for finishing. Main Iron Works has built close to two-dozen boats for Cenac over the years, Molaison added, and the amount of finish work performed by the yard has always depended on the work schedule of the two companies.
Tankage on O.J. Cenac includes 100,000 gallons of fuel in multiple tanks with a common day tank. Fuel is pumped through an Alfa Laval centrifuge filtration system. The centrifuge is also employed to circulate fuel in the tank. Accommodation for a crew of up to 12 people is provided in the traditionally styled three-level deckhouse.
Auxiliary power comes from two Cummins 130-kw diesel generators in addition to a separate Cummins diesel to power the towing winch, provided by Intercontinental Engineering of Kansas City, Mo. The waterfall-type winch has a capacity of 3,000 feet of 2.5-inch wire per drum and 315,000 pounds of line pull.