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Slide On Prop Protector white background

Prop Protector shaft driven rope cutters


What is a Prop protector?

A Prop Protector rope cutter is essentially a cutting blade that fits around your propeller shaft forward of the prop and rotates with the shaft to cut rope or debris that may get entangled in the prop.














The overall diameter of the blade is much smaller than the propeller and ideally should be only slightly larger than your prop hub or stern tube. (The size of the blade is exaggerated in the sketch above.) In other words the Prop Protector, in itself, will not be harmful to marine flora or fauna.


If you have cruised in the US or Europe you may have heard of other makes of prop shaft rope cutters such as the Shaft Shark or Spurs.

It is not the purpose of this article to say that the Prop Protector is the way to go rather to say that some kind of shaft rope cutter is a great insurance policy.  A rope wrapped around your prop can have serious consequences. On a lee shore in a gale, or in foggy shipping lanes it could easily end in disaster. Whether it is a stray sheet tail or an abandoned net, once you lose propulsion, you lose a lot of options.

Two variants

Prop Protectors come in two versions. The Clamp-on version comes in two halves and can be attached around the shaft without the need to take of the propeller. If necessary it can even be installed under water negating the need to slip your vessel.




The slide on version as the name suggests slides over the shaft when the propeller is removed. It has the advantage of being thinner and so can be an option when the gap between the propeller hub and the stern tube is less than that required for the clamp on version.



The Prop Protectors are sized to fit shafts from 20mm (3/4") up to 100 mm (4") and the blade diameter increases from 85 mm up to 150 mm. Some of the more popular sizes have different cutting blade diameters to cater for vessels with larger stern tubes.


  • Suitable for commercial and leisure vessels

  • The original British designed rope cutter

  • 5 year guarantee against faulty materials & workmanship

  • Clamp-On version available for underwater fitting

  • No moving parts to service or fail

  • Cutting action avoids vibrations/shocks often associated with "chopping" style cutters

  • More than 20,000 fitted worldwide

The Prop Protector is NOT designed to be used with outboard engines, stern drive engines or Saildrives.

International Cruising 

Recently we have partnered with Down Under Rally. They organise cruising rallies to Fiji, Vanuatu and Indonesia. For the safety of their rally participants they encourage vessels to have a rope cutter fitted prior to departure. They have a number of stories to recount about incidents involving rope entanglement at sea especially in international cruising grounds.

Even on our home shores here in Australia there are more and more crab pots that can cause headaches. Obviously during the day most are marked and can be avoided but on a night passage with reduced watch keeping and visibility the possibility of encounter is increased.

How to buy
Before you order you will need to know the dimensions of the following components. Refer to the diagram below for information.
  • the diameter of your propeller hub (1)
  • the diameter of your prop shaft (2)
  • the diameter of your stern bearing tube (3)
  • the gap between your hub and your bearing housing (4)
If part of the shaft (4) is tapered then only measure the non- tapered portion. If the non-tapered portion available is less than the width of the cutting blade then it is recommended to purchase a cutter with the smaller diameter bore and get the bore machined to suit. 

Clamp On Prop Protector White background
Slide On Prop Protector white background
Scamatic drawing showing Prop Protector on shaft forward of the propeller
Prop Protector Measurement guide
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