Thruster

In addition to this array of
equipment is the ships thruster,
typically operated by electric
motors controlled from the bridge.

These thrusters are laterally
mounled propellers that can suck
or blow water from port to star
board (i.e. left to right) or vice
versa.

They are normally used only in
maneuvering, e.g. docking operations,
and are often banned in tight confines,
e.g. dry dock.

Thrusters, like main propellers,
are reversible by hydraulic operation.
Small embedded hydraulic motors rotate
the blades up to 180 degrees to reverse
the direction of the thrust.


Taken from wikipedia

ENGINE

An engine room will usually
contain multiple engines,
either diesel or heavy fuel.

The engine are used to provide
mechanical power to the gear
box which speeds up from the minimal
tickover, typically between 400-1000
rpm and a perates the ships hydraulic
pumps , and most importantly,
the screws or propellers.

In addition, it contains the generating
plan normally used to power the ships
electrics.

This often runs on separate engines,
with an array of smaller generators
contributing towards the ships
require power levels.

A margin of error will be allowed,
e.g. a ship requiring 300 amps
night employfour 90 amp generators


Taken from wikipedia