Problem Solving (Failure, Vibration, Performance)

Over the years, CJR has gained a wealth of experience, and we make use of this experience to ensure that any mistakes are not made twice.


Original propeller badly eroded (top image)

and CJR propellers after 3years in constant operation (lower image)

We are therefore in a strong position to offer a problem solving service.
This includes investigating:

  • Vibration levels on board and identifying possible causes
  • Under performing yachts (in speed, turning ability etc.)
  • Excessive cavitation on propellers or rudders
  • Breakage of shafts, propellers and other components

CJR is able to provide ad-hoc and long term consultancy services relating to the longevity and performance of your boat hull and appendages. If you have any problem, get in touch, we are here to help.

Cavitation erosion problem on Hythe ferry propellers

Back in year 2008, White Horse Ferries, operators of Southampton’s Hythe Ferry, approached CJR Propulsion to provide consultancy services relating to a recurring and expensive problem with its existing propellers. An issue with cavitation and erosion was so severe that the propellers had to be replaced on an annual basis – causing disruption to service, as well as significant replacement costs. We had investigated why the cavitation was happening so rapidly while the boat was out of the water. We found out that the ferry had double shaft and keel supports, placed very close to the propellers – which were a hangover from the boat’s previous life. They were not needed for her current operation and were poorly positioned in terms of propeller operation, so after some initial calculation, we made the decision they should be removed. We also designed and manufactured propellers for the boat. After 4 years of operation the boat was being serviced in Saxon Wharf and we had a chance to have a look at the sterngear. There was not a single cavitation mark on propeller blades - a very positive result!

Pilot boat shaft failure problem

One of pilot boat operators at Solent area turned to us in 2011 seeking for a solution to a problem with propeller shafts failure and excessive wear of flexible couplings. The boat was in constant use and the operator kept replacing shafts on periodic basis - every 18months.  CJR investigated the issue and ruled out eventuality of shaft diameter being too small at the beginning. Shaft breakage area was indicating that bending moment had bigger part in failure than engine generated torque. We focused on more holistic approach in that case - flow around the hull was investigated, inflow to the propeller was assessed including propeller generated excitation forces and shaftline itself was put under scrutiny. As a result P-bracket downward looking skegs were removed as being too close to propeller blades. Also one of 3 shaft supporting bearings was removed to make the system more flexible and less susceptible to vibration. Propellers were lapped to the shafts and the boat was back in the water with new flexible couplings. We have never heard of any problem with the shafts since.

  • Bearings

    Suitable bearings are required in stern tube and rudder tube assemblies.

  • CJR Propellers

    Every boat is different and the first sign of this difference can be seen in propeller operation.

  • Couplings

    Couplings are the elements that transfer torque from gearbox to the shaft and because of their role they are under strict supervision of class societies.

  • Ducted Propellers / Nozzles

    CJR can offer ducted propellers systems including any type nozzles and impellers under full IACS approval.

  • Rudder Tubes Assemblies

    CJR manufactures rudder tube assemblies designed for hull trough installation to suit stock diameter from 30mm up to 180mm.

  • Rudders

    Rudder profile and sections are carefully selected to specific regime of the flow around sterngear.

  • Shaft Brackets

    Our shaft brackets are designed bespoke to achieve optimum performance in line with every vessel individual requirements.

  • Shaft Seals

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  • Shafts

    Shaft design starts from designing entire shaftline incorporating all the components from the propeller to the gearbox and including the bearings to make the system safe, vibration free and efficient in operation.

  • Stern Tubes / Shaft Logs Assemblies

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  • Tie Bars

    Tie bars connect both rudder tillers on twin rudder boats to simply synchronise them together.

  • Tillers

    Tiller is important part of steering gear which design is covered by strict rules of classification societies when the boat is built under class.

  • Shaft Alignment

    Using laser technology and precision engineering a bespoke shaft alignment tool has been developed to aid the boat builder’s task of accurately fitting and aligning the stern gear.

  • PropSmith

    For the fast, simple and precise installation and removal of propellers, PropSmith is the professionals’ choice.

  • TrialDAS

    TrialDAS is a new data acquisition system specifically tailored for monitoring sea trials. The system is based on rate gyros, GPS, accelerometers and magnetic field sensors to record every movement of the boat.

  • Keyless Hub Hydraulic Kit

    Quick and convenient method of pushing and releasing large propellers or couplings to and from the keyless shaft cone.

  • Hydraulic Propeller / Coupling Pusher / Puller

    Quick and convenient method of pushing and pulling propellers or couplings to and from keyed shaft end.

  • TrialsAPP

  • Quality Policy

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  • Design

    We don’t only make propellers, we analyse entire propulsion system of each boat starting from hull resistance prediction and hull propulsive factors.

  • Pattern Making

    Precise pattern assures high accuracy of final product and it is one of the most important stages in manufacturing process

  • Casting

    CJR's foundry team has the combined benefits of over 150 years experience in the industry.

  • Machining

    CAD/CAM controlled machining of the cast propellers, P brackets and rudders are undertaken to the fine tolerances of their original design

  • Finishing

    Our processes ensure that the geometry of our finished castings is always true and accurate to the original design.


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CJR Propulsion Ltd
70-72 Quayside Road
Bitterne Manor
SO18 1AD
United Kingdom

Tel: +44 (0)23 8022 2032
Fax: +44 (0)23 8021 1832