The engineers were manning and running the technical systems on board.
That included main motors, generator, batteries, diesel engines, HP air equipment, fans, air purification, sanitary system, breathing apparatuses, bilging and tanks etc.

One important mission was to look after the batteries and this responsibility fell on the first engineer. The battery was treated like a baby as it required the same attention. The submarine performance was highly dependent of its battery status. 

Many machinery solutions were genially simple and had their roots in the early century submarine technology

A frequent operation on the diesel engine was hauling of its pistons. In such a case the piston had to be lifted out for cleaning and checking of the piston rings.

The submarine had three engineers and 6 motor men. They represented a broad spectrum of experience. The motor men had ship numbers 16, 21, 32, 33, 35 and 36 and some variation in ranks.

Submarine U3 Diskussion in front of the diesel engine.
U3 Diskussion in front of the diesel engine. Photo U3 archives.

Submarine U3 The diesel engine under repair.
U3. The diesel engine under repair. Photo Rune Nilsson.

Submarine U 3 engine room.
U 3 engine room. Photo U3 archives.