Bruntons Sigmadrive Coupling


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 Bruntons sigmadrive selector

What makes the Bruntons Sigmadrive Coupling different is its ability to resist propeller thrust when installed as a standalone coupling, directly from the shaft to the output flange on the engine’s transmission. It reduces and even eliminates vibrations that originate from an imperfect alignment between the propeller shaft and the engine, compensating for up to 3 degrees in all directions. This system can also be installed using thrust bearings so that the engine can be placed utilising the space available ergonomically


The Sigmadrive SD55 is for conventionally driven vessels. The system uses a constant velocity joint to self-align the shaft. Thrust taken up on the engine from the propeller invariably changes the angle of the shaft line, particularly when the engine uses soft rubber mounts. Using a single SigmaDrive replacement coupling will ensure the shaft is correctly aligned at all times, especially under high load. The result, reductions in many cases of around 50% in noise and vibration.

The SD55 standalone unit that resists the propeller thrust compensating for up to 3 degrees in all directions.

Manufactured from a special Aluminium Bronze, SigmaDrives are a premium product requiring virtually no maintenance and containing no bearings or rubber in their construction. In addition to requiring little maintenance themselves, fitting one also means considerably reduced maintenance will be necessary on other stern gear components.

  • Compact size, comparable to a standard shaft coupling.
  • Provides perfect alignment for the propeller shaft and works perfectly in line or out.
  • Easy and quick to fit, usually without slipping the vessel and without the need to modify the propeller shaft, or fit fixture plates or brackets for thrust bearings that are no longer required.
  • Contains no rubber or bearings, and is manufactured from a special alloy that ensures long life with little maintenance required.
  • A highly cost-effective solution requiring little or no costly modifications to the vessel.


Suitable for Engines from 5hp to 100hp. Dependent on RPM and Gearbox reduction.

Available for  Metric & Imperial shafts sizes between 25mm and 1-1/2″ range.

Price: £389.50+Delivery & VAT. Includes most Standard 4″ Gearbox Adaptors. (May require adaptor depending on gearbox type)

Example of standard 4″ Gearbox Adaptors – PRM, HURTH, BORG WARNER, TMC, ZF, YANMAR & VOLVO*


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