Marine Engines

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This subject spans many decades...

PRESENTING THE

DETROIT DIESEL INLINE 71 SERIES

In the late 1930s the brilliant engineering design team at the GM Research Laboratories, led by Charles Kettering, set out to develop a versatile small high speed diesel engine that would be suitable for a wide range of automotive, marine, and industrial applications. The result was the GM Detroit Diesel 71 series, one of the most successful and long lived diesel engine designs ever produced. The 71 series engines are named for their swept displacement per cylinder (in cubic inches), a naming practice that Detroit Diesel also shared with the Electro-Motive Division of General Motors.

The main incentive for the development of the 71 series was GM's truck production and their partial ownership of Yellow Coach. This provided an immediate market for thousands of the engines, but the designers also made advance provision in the design to accomodate marine exhaust manifolds, pump and power takeoff units, a wide range of engine mountings, generators, and marine transmissions. Consequently the engines could also be used for an impressive variety of marine or stationary power generating, power takeoff, and pumping applications.

The 71 series are two-stroke cycle uniflow scavenged engines, with the air entering the cylinders through a ring of ports in the cylinder liners, and the exhaust exiting through valves in the cylinder head. In early production all the engines were fitted with engine-driven Roots blowers, but late production some models of the 71 series were available in versions having a turbocharger in series with the Roots blower for higher power output.

Eventually the series would be built in one, two, three, four, and six cylinder inline models. The four larger engines were well equipped for use as ships service engines on tugboats, and the 4-71 and 6-71 were often used for propulsion in smaller tugs and workboats, singly or in twin or quad sets. When the US entered World War Two, the 71 series diesel were adapted to many military applications, including propulsion packages for tanks and use in landing craft, ships' boats, and shore based power generating plants. Following the war the two cylinder 71 was often used as a refrigeration engine in railroad cars.

The 71 series served as the design model for a number of other engines, both larger and smaller. In 1945 GM introduced the larger but very similar 110 series uniflow scavenged engine, which proved successful in many marine and railcar applications. There were both Roots and centrifugal blower versions of the 110 engines. Around the same time they introduced the smaller 51 series valveless cross flow scavenged engines. The 51 series was built in small numbers, primarily as a marine and industrial engine, and today they are very rare and eagerly sought by engine collectors. The 51 series was replaced in the product line by the more conventional 53 series uniflow scavenged engines in the 1950s, which was used in a wide range of marine, railroad and industrial applications as well as in trucks. Vee versions of the 71 series were also developed in this time period, and became a very common bus, marine, and power generating engine for several decades. The Vee 71 series eventually included six, eight, twelve, and sixteen cylinder models. The product line was further supplemented by the very similar but more powerful 92 series engines, basically a larger bore version of the 71s, which remained in production until very recently.

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

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Above: A longitudinally sectioned view of the Detroit Diesel 3-71 engine shows the view in the air box (left to right) of the outside of the liner on cylinder #3, a section through the piston and rod on cylinder #2, and an outside view of the piston, rod, and rings on cylinder #3. Top three illustrations by GM Diesel Power.

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Above: The Detroit Diesel 71 series was stunningly successful right from its introduction, and engine #100,000 was produced by the middle of World War Two. The production life of the 71 series was from the 1930s into the 1990s, making it one of the longest manufactured and successful diesel engines of all time.

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Above: The engine room of a newly completed tugboat photographed in the early 1950s shows the typical application of Detroit Diesel 71s along the port side as ships service engines, with a Cleveland 12-278A main engine. From the 1930s into the 1950s, GM Diesel Power served as the marine and industrial sales agency for all the GM divisions building diesel engines, including Detroit Diesel, Cleveland Diesel, and Electro-Motive Division. Under this arrangement, vessel sets of engines were often sold and installed as a single order. This photo is from a Cleveland Diesel Engine Division publicity package issued at the vessel launching.

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Above: A pair of Detroit Diesel 71s are shown in the engine room of a Lehigh Valley Railroad tug at Jakobson Shipyard in the late 1940s. The electrical switchboard is aft of the two engines behind the access ladder to the main deck. Photo from a Cleveland Diesel Engine Division press package.

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