44 July 13, 1998

Dutra Dredge Twins Enviro Engines

In 1995, Dutra Dredging 65-foot pusher tug "Sara Reed" was powered by a pair of eight-cylinder two stroke diesels. One had recently been rebuilt and the other was getting tired. To replace the worn engine, the owners were looking for something with a longer life expectancy and found what they were looking for in a four stroke twelve-cylinder Cummins KT38 rated at 800 hp. Now, after more than two years and 10,000 hours of the two engines running side by side, the Cummins is still going strong but the rebuilt two stroke is giving out. The company has had an opportunity to compare the operation of the two stroke and four stroke technology and the product of two leading manufacturers.

The results are in, and Dutra have installed a second of the Cummins 38 litre engines. This one, the after cooled version designated KTA38 with a potential of 850 hp at the continuous rating. The new engine is also equipped with the ST or Step Time system by which the timing of the fuel injection is modified by the increase in oil pressure as the engine RPM increases. Dutra's Maintenance Superintendent Dave Martinez has decided to run the boat with the original Twin Disc MG530 gears for now and is looking to get at several more years out of the original Cummins engine and a good bit more from the current installation. Martinez points out that, "In all fairness you can't compare the older engines with these new generation engines. If you look at the smog emission and environmental regulations that we face today, you see what the manufacturers are trying to do in reducing fuel burned and emissions created."

On their various dredges and boats Dutra operates up to 300 diesel engines each of which they select to meet a widely varying set of criteria. Currently two of their big new hydraulic diggers are operating in Newark New Jersey and Miami Florida. "We have some of the big Cummins K50s on those," says Martinez. But it is the equipment working in the San Diego California environment that gets the greatest scrutiny by State officials looking to reduce emissions. "We are only allowed so much emission per rig," he says, "Otherwise we'll be shut down. Today engines are being built to meet those specs. Manufacturers have to be conscientious about efficient fuel consumption."

Fortunately for Dutra and the pusher tug "Sara Reed", the current generation of engines is able to meet these demands. At the same time Martinez says they shopped around on other engines and in the end it was the willingness of Cummins people like Tom O'Conner and Tom Thompson to go "that extra mile" that clinched the decision.

A note to editors, this might prove to be a story worth following up for an actual working test of two stroke versus four stroke technologies in marine applications.

For further information:

Steve Martinez
Dutra Dredging
Rio Vista, Calif.
Phone: 707 374-6964 Fax: 707 374-6039

Tom O'Conner
Cummins West Inc.
1601 Aurora Drive
San Leandro, CA 94577
Phone: (510) 351-6101 Fax: (510) 614-9159

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