service? (Вариант из мультитрановского морского словаря для "службы")

Относительно судовых механиков: взгляните на приведенный внизу линк

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Note added at 2002-03-26 05:28:52 (GMT)
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**ENGINE DEPARTMENT**
The engineers are responsible for the highest light on the main mast to the lowest pump in the bilge, and everything mechanical in between. In short, they keep the ship running smoothly.

**Chief Marine Engineer** Edgar Figueiredo
1st Assistant Engineer Harry Erickson
<...> (http://www.pmel.noaa.gov/tao/kaimi/staff.html)

То есть, получается, что Вашего персонаже можно назвать либо

Head of Engine Department либо
Chief Marine Engineer

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Note added at 2002-03-26 05:34:44 (GMT)
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There are three main areas in merchant navy

deck department,

engine department

service department

<...>The second department is the engine department responsible for installation or repairing of ship engines, supervising and the mechanical and electrical work. This department consists of the chief engineer, radio officers, electrical officers and junior engineers, who also coordinates the activities of the engine and the room crew.
http://www.schoolcolleges.com/career/mnavy.htm