Repower rethink keeps veteran tug working

Catherwood Towing has grown up around log towing in Canada’s Fraser River. The work, known as ‘yarding’, generally employs boats in the 25 to 43 foot range. Catherwood has several of these boats, most powered by twin Cummins KTA19 engines.

To diversify their operations, Catherwood has been doing more barge work and now has contracts to tow gravel from a quarry about 30 nautical miles north of the Fraser River. The company has also picked up a couple of freight runs towing barges with truck trailers. To better serve these contracts, the company has purchased some larger ‘outside boats’ as the opportunity arises. Such was the case when the owner of a 74 foot boat phoned Ernie to see if he was interested in adding to his fleet.

The 39 year old boat was at a shipyard undergoing a scheduled Canadian Steamship Inspection. Ernie had marine surveyor Mark McAllister and his port engineer, Trevor Sexton, check the boat out. They reported it to be sound, with excellent half-inch hull plating. The old 12V149 GMC engines were tired but their big Lufkin gears had recently been rebuilt and were in good shape.

Ernie decided that if he could repower the boat with a new set of Cummins KTA38 engines at the right price, he could make some money with the tug. Todd Braconnier of TCB Marine Consulting proposed that they use a well proven process of installing the new engines through the side of the hull rather than the traditional lowering in from above and moving forward into the engine room. Mark McAlister explained that design forethought by the builder in placement of tanks and auxiliary machinery on the tug made this method much simpler.

“We were able to do the engine swap with this method for half the cost of stripping the engine and going in from the hatch in the aft deck, Catherwood said, “The savings in labour, with workers not climbing up and down to the main deck, are significant but more importantly, the crew at Arrow Marine terminals, where we are doing the job, were able to remove the old and set the new engines in place with a fork lift. With long forks, even the starboard engine, opposite the hull opening, could be set.”

The engines were coupled to the existing air-controlled Lufkin gears that are each nearly the size of the engines. In addition to air-clutches, the gears have air-controlled shaft brakes. The 7:1 reduction allowed Catherwood to keep the big 84 inch, three blade props that turn in Kort nozzles.

In addition to the main engine repower, Catherwood has installed two new 50 kW gensets, upgraded the electronics included 40 wheelhouse alarm sensors for the engine room, done a complete overhaul of the Burrard towing winch and rebuilt various components and piping. The winch is fitted with an air-controlled brake and carries 2,400 feet of 1.25 inch wire. For Canadian manning and regulatory reasons, Catherwood will set the new engines for only 500 hp each, but the bigger boat, renamed DD Catherwood, with its powerful gear and prop combination, will do much to assure ‘just-in-time’ delivery on the company’s chartered freight runs regardless of weather conditions.