Workers in this unit group operate and maintain ships' engines, boilers and mechanical equipment on vessels afloat, usually under supervision of engineer officers. Their functions include: tending one or more boilers producing steam for ships' engines; lubricating bearings, moving parts of engines and other mechanical equipment on board ship; assisting engineer officers and engine-room mechanics in repair and maintenance of ship's engines and mechanical equipment; performing related tasks. Ships' engine-room mechanic is classified in 8-49.90.