Old Tugboat Engines

A Place For Fun With Old Engines

This subject is from the 1940s...


Cooper Bessemer was one of the major US based builders of large marine diesel engines for many decades. The company, based in Mount Vernon, Ohio, dated back to the 1830s and was a major builder of steam engines for industrial and agricultural applications, with the Cooper Bessemer Corporation name dating to the late 1920s. After 1965 the company was known as Cooper Industries. It is now a component of Cameron Corporation.

The Cooper Bessemer Type LS was a large direct reversing four stroke cycle marine engine with 15-1/2 inch bore and 22 inch stroke, built in six, seven, and eight cylinder configurations, and in naturally aspriated and turbocharged versions. Power ratings of up to 1400 horsepower at 400 RPM were available from the eight cylinder naturally aspriated unit, and outputs up to 2100 horsepower at 400 RPM could be achieved by the turbocharged eight cylinder engine. For marine applications, the engines were equipped with an internal Kingsbury type thrust bearing housed in an extension of the engine frame and lubricated by the engine main lubricating oil system.

The very heavily constructed Cooper Bessemer Type LS engine incorporated some novel construction features, including a cylinder block built in sections, that was bolted to a full length engine base that supported the crankshaft, main bearings, and bearing caps. The design of the engine reciprocating components was unusual, with five compression rings and three oil scraper rings all mounted on the piston above the bossing of the piston pin. The liners were wet type, with rubber seals at the top and bottom. Other design features were in common with typical large marine and stationary engines of the period, including the mounting of the intake, exhaust, and air starting valves in removable valve cages. The injection valves controlling admission of fuel to the cylinders were mounted in clusters on the "operating" side of the engine (where the controls are located) and cylinders could be cut out individually if needed.

The Type LS engine was developed in the late 1930s and was widely used through the 1940s and into the 1950s, its applications included military vessels such as Army LT tugs as well as commercial tugs, passenger and cargo vessels.

Article and page design by Preston Cook, ©2009 by T.E.S.


Above: This is a view of the exhaust and intake side of the six cylinder version of the Cooper Bessemer Type LS diesel engine. This version of the engine typically was rated at 1000 horsepower at 400 RPM.


Above: This is the "operating" side of the six cylinder Type LS marine engine showing the gauge panel, the governor in the center of the engine, the single lever operating control for both speed and reversing, and the connecting rack linkage between the governor and the two blocks of fuel injection control valves.


Above: Cooper Bessemer was one of the earliest US users of turbocharging, which typically increased engine output from 30% to 50%. This would allow the large eight cylinder version of the Type LS engine to produce as much as 2100 horsepower at 400 revolutions per minute operating speed.


Above: This view shows the intake and exhaust side of the eight cylinder turbocharged version of the Cooper bessemer Type LS marine engine. The exhaust manifold leading to the turbocharger is fitted with a heat shield, and the intake manifold is much larger diameter than on the naturally aspirated engine. There appears to be no aftercooler for the turbocharger. The engine driven air compressor for starting and control functions is mounted in the middle of the side of the engine.


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