Sigma Drive- Avoiding Propeller Shaft Misalignment

It is of utmost importance to have a well aligned propeller shaft in a boat, else it may lead to heavy vibration and noise leading to efficiency reduction and in extreme cases failure of shaft components. The alignment of the shaft can be achieved through a constant velocity joint connecting propeller shaft and boat engine.

What is Sigma Drive?

It is a constant velocity joint coupling which allows power transmission between engine and propeller shaft at variable angles but at a constant speed. It also performs two main functions:

  • Rotates the propeller shaft without transferring engine vibration in the propeller shaft.
  • Resists propeller thrust going to the engine without the need of thrust bearing.

 Features of Sigma Drive

It is a constant velocity joint manufactured from alloy of bronze which enables it to withstand the heat generation and provides a long service life with less maintenance.

It helps in self alignment of propeller shaft which is passing through rubber bearing and shaft seals to increase the working life of all propulsion system.

It can be used from engine lying in range of 10 bhp to 1300 bhp and claims to be the only such system that can be used in V drive gear box.

It also acts as an angular corrector with a deviation limit of + 4 ̊.


  •  Compact in size as compare to other mountings and easy to install.
  • No modification of propeller shaft or other drive system needed.
  • It can be fitted in direct as well as v drive propeller shafts.
  • It eliminates the requirement of thrust bearing.
  • Made up of bronze hence equipment in antioxidant and ideal for marine use.
  • Can be fitted in both new and refit vessel.
  • Almost eliminates vibration from the normal running system.
  • Reduces noise level.

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  1. Please send me an e-mail describing your propulsion system (engine-gearbox-shaft) , where you are from and I will reply to your question.
    Best regards

  2. I installed a sigma coupling on a fishing boat the engineer assured me it would be fine that was 6 months ago it has failed when I took it off to inspect it it was bone dry. When I sent it back to the manufacturer they said it was uncommen for the to fail I was just wondering if any one else has had any bother with them

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