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Drivetrain and Propulsion Overhaul and Dry Dock Support


Type of project:  

  • Remove port and starboard gearboxes for overhaul
  • Remove rudders and propellers
  • Remove starboard companion coupling. 
  • Check run out of port and starboard prop shaft
  • Reinstall all components, including rudders, propellers, prop shafts, couplings and gearboxes
  • Laser alignment of starboard and port gearbox, including moving of engine to ensure alignment.

Customer Name: Technical Managers of a small passenger vessel

Location: Belfast, Northern Ireland

Initial Enquiry: 

We were contacted by a technical management company for a Scottish passenger cruise vessel to assist with the removal and repair of the vessel’s starboard ZF 2250 gearbox. The issue arose after the ship ran aground, causing the propeller to be damaged and the output shaft to shear off. The technical managers also requested that we check the port shafting arrangement while our engineers attended to ensure there was no issue with this side of the propulsion system while the vessel was in dry dock. MIT also proposed to manage the repairs of damaged propellers and rudders.

Project Description: 

Before work commenced, our Marine Sales Engineer discussed the issues with the technical management company to better understand the vessel’s problems and determine the scope of work required. Upon discussion, it was identified that not only did the starboard gearbox need repairing following the shearing of the output shaft, but the port side ZF gearbox also needed removal for overhaul. In addition, the port and starboard propellers and rudder were damaged and in need of repair, so as part of the scope of work, MIT was asked to manage the refurbishment of these.

Following the scope of work discussion, it was decided that the first step would be to send an engineer to remove and uplift the gearboxes for overhaul. Once the removal was completed, our team could begin work on the propellers and rudders.

Gearbox and Shaft Removal

Upon attending the vessel, our engineer assessed the gearbox removal, using the provided vessel plan to identify the lifting eyes and route for removal of the gearboxes. The gearboxes were drained, and electrics, hoses, and ancillary components were disconnected. The starboard and port gearboxes were removed and palletized along with their associated components for uplift. During this process, our engineer checked the alignment on the port side and found it to be within tolerances.

Propeller and rudder repairs

After our engineers successfully removed and uplifted both port and starboard gearboxes for overhaul, the team began removing the rudders and propellers for refurbishment following the damage. Once removed, they were sent to our approved partners for surveying before the required repairs were made to all blades and the rudder. Following the repairs, they were approved by class and balance tested before being uplifted and returned to the vessel for reinstallation.

While removing the propellers and rudders, our team also carried out a run-out check on the vessel’s port and starboard inboard and outboard prop shafts. Upon inspection, it was found that the run-out was out by 0.28mm, which meant that the prop shaft had to be removed for further investigation and lathed. In addition to this work, we removed the damaged starboard inboard companion coupling that had been caused by the tail shaft shearing and replaced it with a new one upon the return of the prop shaft. Finally, we removed the port and starboard prop shaft seal box gland packing before installing the new one.


Gearbox and Shaft Reinstallation

Once the gearboxes were overhauled, our team returned to the vessel to refit the starboard tailshaft, new couplings, propellers, rudders, and the overhauled gearboxes. As part of the gearbox installation, we checked the alignments and found that the port side was within tolerance. However, the starboard side was found to be massively out of alignment, which meant that the engines had to be lifted and the engine mounts removed to have them machined to allow our team to move the engine and gearbox over by the required amount to ensure correct alignment. Following this, both gearboxes were tested to ensure they were functioning as they should be.



In conclusion, our team successfully carried out the removal and overhaul of the starboard and port gearboxes, as well as managing the repair of the propellers and rudders. Additionally, we checked the run-out of the port and starboard prop shafts inboard and outboard and removed the damaged starboard inboard companion coupling. Finally, we reinstalled all components, including the gearboxes, rudders, propellers, prop shafts, couplings, and sealbox gland packing. As part of the reinstallation process, we carried out laser alignment of the starboard and port gearbox and moved the engine to ensure correct alignment. We are pleased to have been able to assist our customer and ensure that their vessel is now fully operational.



Contact Us:

If you require similar repair and maintenance services for your maritime assets, please do not hesitate to contact MIT. Our experienced team stands ready to deliver outstanding results for your upcoming projects, ensuring your vessels’ continued reliability and safety.

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