The S-boot motor, like the boats themselves, underwent a constant evolutionary process stressing individual quality and survivability over the production of large quantities of expendable materials. As the boats were adapted to operate in increasingly harsh combat environments, increases in engine performace were necessary to counter the growing weight of armor protection and anti-aircraft weaponry. While the first S-Boot powerplant produced 900 hp, the final production type produced a herculean 2,500hp. A 3,000hp S-boat motor was in the final stages of development when Germany capitulated. (By comparison, the DB 601a engine, standard equipment in the Bf109e single engine fighter produced 1,000 horsepower).

S-boats were configured with three diesel engines driving three prop shafts. Specially developed MAN and Daimler Benz engines were fitted in the early S-boats. Although equal in horsepower, the in-line MAN motors tended to produce excessive vibration, and had a high center of gravity. This led to breakdowns and unacceptable stresses on the boats' light motor mounts. In 1938 the Naval staff decided upon the reliable 20 Cylinder 2000hp MB501 V-engine as the standard S-boat powerplant. The MB501 proved highly dependable and a versatile basis for later improvements such as the addition of superchargers. The final versions of the MB501 could propel the 100 ton boat to speeds of 43.8 knots.

Situated in the middle of the hull, the engine room reflected thorough German planning and smart design inherent in the entire S-Boat program. Although noisy, it was spacious, well ventilated and illuminated by skylights. Conduits and wiring were neatly laid out to allow accessability for quick identification and repair. The risk of fire was greatly diminished by the use of diesel fuel and by a built-in Ardex fire extinguishing system. Aircraft style instrument panels monitored performance of the three engines. Instructions from the bridge were recieved on a miniature engine room telegraph.

Although the engines were technological marvels, it still took well trained crewmen with steady nerves to keep them running.

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Mechanic monitors instruments. On his right, the engine telegraph

Facing the bow in engine room, a view of the starboard engine. Instrument panel in center.

View aft in engine room. A cylinder is serviced.

View of instrument panel and Daimler-Benz engine, facing aft in an early boat.

Instrument panel & engine telegraph in late war boat (USNA courtesy Chip Marshall)

Engine intake and exhaust conduits (USNA courtesy Chip Marshall)

Detail of the engine room telegraph which transmitted orders from the bridge. A visual indicator was necessary due to engine noise

MAN engines. Their height was a disadvantage.

20 cylinder MB501 engine, crated for delivery.

Another view of the MB501 engine.

Color view of a MB501 being refitted in Norway.

Engine cooling water intake and exaust ports. (USNA Courtesy of Chip Marshall)

Engine room of salvaged late war boat. (USNA Courtesy of Chip Marshall)

Engine air intakes, midwar. Notice the shutter grille.

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