Bow and Stern Thrusters are now considered essential pieces of propulsion equipment within the shipping industry, as they provide additional manoeuvrability.  This is particularly useful during challenging operations like docking and some offshore operations.  Thrusters also assist vessels to dock independently, which can, in some situations eliminate the need for tugboat assistance.
 

What are bow and stern thrusters?

Bow and stern thrusters are transverse propulsion devices. They operate independently of the main propulsion system.  Modern ships tend to use tunnel thrusters. These are built into the bow or stern. They are positioned below the waterline but ships with thrusters generally have some sort of indicator of this above the waterline. This is usually a red X.

Thrusters do have the potential to create undesirable resistance while the ship is in forward motion. This can, however, be mitigated by ensuring that the tunnel aperture is properly faired aft.

How bow and stern thrusters can be maintained

All bow and stern thrusters should have a grill in front of them. This will limit the amount of debris that can get into the tunnel and/or impeller. Not with standing this, thrusters will still need periodic cleaning.

The space heater should be checked regularly. This is important to keep the insulation dry. For the same reason, you should check for leaks in the bow thruster room. These usually indicate a damaged seal. The insulation itself should be carefully monitored. If it starts to get damaged by moisture, you need to find out before the next time you need to rely on your thrusters.

Once a month or thereabouts you should check and grease the motor and links. You should also test for water in the hydraulic oil and check the thickness of the contractors.  
 

How bow and stern thrusters can be repaired

More in-depth maintenance and basic repairs can be done while the ship is in dry dock. It might be possible to keep the thrusters on the ship. If not, they will generally only be transported to a nearby warehouse. This kind of work is usually undertaken as part of a planned dry dock.

How bow and stern thrusters can be overhauled

When bow and stern thrusters need a major overhaul, they do need to be disconnected completely from the ship. This allows the thrusters to be stripped back to their components for in-depth cleaning, repair or replacement.

All thrusters will need a major overhaul from time to time as components do wear out through use. The number and frequency of major overhauls can, however, be kept to a minimum through proper maintenance and repair.