Checklist for skippers: Everything you need to know about the propeller

Read more at YACHT:

• ​Rope in the propeller: the key steps to take in an emergency
• ​After the line gets caught in the screw: This needs to be checked
• ​Protecting propellers: How skippers can prevent damage to the propulsion system

Text: Nico Krauss; Updated by: Antonia von Lamezan, 7 August 2026

Not all damage is caused by a collision. Often, it is inconspicuous factors that cause the drive system to wear out over a period of months or years.

• Electrolysis and lack of anodic protection: Corrosion affects the propeller and shaft if the sacrificial anodes are worn out or unsuitable.
• Floating lines and ropes: Mooring lines, tow lines or sheets that have fallen overboard can wrap round the shaft in the blink of an eye. Floatable lines for the dinghy reduce this risk.
• Nets and fishing lines: Thin strands of string often find their way onto the shaft without being noticed. They can work their way right up to the oil seals and cause damage to the shaft seal there.
• Plastic bags, jerry cans and wood: Even seemingly harmless objects can block or damage propellers.
• Basic touches: Yachts with fixed propulsion systems, in particular, are at risk if they come into contact with the seabed.
• Vegetation: Barnacles and seaweed impair the flow, increase fuel consumption and reduce performance.
• Wear and tear on folding propellers: Open gear teeth wear down over time and must be checked regularly.
• Lack of maintenance: Corrosion, worn-out bearings or loose fastenings often go unnoticed for a long time.
• Operating errors: Frequent or sloppy gear changes put unnecessary strain on the gearbox and drivetrain.
• Incorrect assembly: Propellers that are not secured properly may come loose or cause further damage.

Check the drivetrain regularly

Many problems can be identified during routine maintenance before they lead to more serious damage.

• Visual inspection for cracks, damage and corrosion
• Remove fishing lines, bits of rope and other foreign objects
• Cleaning and greasing the propeller
• Clean and lubricate the open gear teeth of folding propellers
• Replace the shaft seal approximately every six to eight years
• Check the shaft end bearing for play. If the play is between 0.5 and 1 mm, the shaft end bearing must be replaced
• Replace sacrificial anodes when they are about half worn, at the latest
• Check the propeller mounting (crown nut and split pin)
• Raise the crew’s awareness of the dangers in the water and the need to handle the gear system with care

What to do in an emergency

If the engine speed suddenly drops whilst you are driving, or if you experience unusual vibrations, this is often caused by a foreign object in the propeller. In this case:

• Disengage the clutch immediately.
• If possible, do not restart the engine.
• Investigate the cause.
• Always keep the boat ready to sail.
• Set sail and sail clear of the mooring wall or the fairway.
• Ask the harbour master or a pilot boat for towing assistance via VHF or mobile phone.
• Prepare the towline and brief the crew.
• In the event of immediate danger, call for assistance on VHF channel 16.
• If necessary, hoist the Foxtrot flag (white with a red diamond) as a signal that the vessel is unable to manoeuvre.

Essential equipment for emergencies

Certain items of equipment can help to minimise damage or make rescue operations easier.

Rope cutter

The idea is as simple as it is effective: cutting blades mounted on the shaft are designed to cut through fishing line, seaweed or plastic immediately, before they become entangled around the shaft.

In practice, however, the effect depends heavily on the propeller design, rotational speed, material and size of the foreign object. With larger ropes, so much rope often becomes wrapped around the shaft that even a cutting system reaches its limits.

Basic rope cutters cost around 100 to 400 euros and are relatively straightforward to fit as an aftermarket addition.

The “Spurs Line Cutter” It uses a different cutting principle and is designed to offer better protection against chipping. However, it is considerably more complicated to fit, and the price is around 900 euros.

Spare propellers and diving equipment

If you’re planning longer trips, having a spare propeller can often save you a lot of time in the event of damage. In an emergency, a simple fixed-pitch propeller is usually sufficient; there’s no need to keep an expensive folding or variable-pitch propeller as a spare.

Also worth having on board: a diving knife, a wetsuit, a snorkel and a diving mask. Under the right conditions, these can often be used to remove small foreign objects yourself.

Good seamanship makes all the difference

Technical aids can reduce the risk of propeller damage, but they are no substitute for good seamanship. The key factors are neat line handling, a boat ready to sail, regular maintenance and a crew who know how to react in an emergency. If you bear these points in mind, you will significantly reduce the likelihood of costly damage to the propulsion system.