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Dealing with a fouled propeller



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What is the issue?
Occasionally you will get a rope (most likely your own), or netting or a bag, around the propeller that will affect propulsion. Or, as is often the case, a mooring line that will serve to tether the vessel to the spot.

Why address this?
The prop needs to be cleared to get underway and make the boat manageable under power.

How to address this?
Clearing a fouled propellor is a non-trivial task. It has only happened to me once and that was a pair of grain bags that wrapped around my propellor as I was exiting Casablanca Harbour. Cutting away the hundreds of strands whilst overhanging the boats counter stern was a difficult, arduous and dangerous task.

I discovered then why people carry line cutters that are capable of cutting right through trailing lines. Typically, these units are stainless disc/blade cutters secured to the prop shaft just forward of the propeller. But sometimes it is good to retrieve the odd line intact that goes around a prop, and we should try our best to retrieve the odd lobster-pot line that we picked up, so as not to impair a fisherman's livelihood. So if you foul your prop without a cutter installed, here are some steps you can take to try to remedy it.

FOULING SITUATION

Once you discover the prop has been fouled stop the engine immediately and try to make the best of the situation to resolve the issue:

  • • If drifting free in safe settled waters, where it is possible to safely drift for some time, do that.

  • • Alternatively, if it is safe and possible to anchor this would be the better option.

  • • If close to a safe easily accessible anchorage hoist the sails and sail in there where it easier to deal with the task of freeing up the fouled prop.

  • • If there is some wind and seaway it is a good time to hoist the sails and 'heave to' in order control the vessels movement and slow forward progress, as well as fixing the helm and sail positions so that the boat does not actively have to be steered.

  • • If the boat has sail up and is held or anchored in place by a mooring line you need to take the pressure off the part of the prop or the rudder as the case may be. Drop your sails immediately.

  • • If, on the other hand, you are in imminent danger of grounding or drifting ashore put an anchor out. It is advisable to notify the coastguard of situation. Try flag a nearby boat that may be able to tow you to safety but make certain to pass them your line in order to avoid any salvage issues.


What you need to do is provide yourself with some time and more sheltered conditions to resolve the issue. This could be resolved with a little time and effort if you are lucky, and quite some time and effort if you are not.


IF YOU ARE LUCKY

If it is a solid line, such as one of the boat's lines that has gone overboard, get hold of the end or have someone hook it up. Then pull on the free end whilst a second person goes down below and rotates the propeller shaft by hand in the opposite direction from which it was turning when the line was pulled in. If you are lucky the line might simply unwind back out.

Failing that, if it is a free line and not a mooring line or lobster pot, start the engine in neutral and using low revs briefly push into reverse - do not rev the engine hard as it is only likely to wrap the line more tightly around the prop. Sometimes, and again if you are very lucky, this alone can unwind and throw the rope or object off. If you have the end of the line, pull on it but do not wrap it around your hands – you’ll need to let it go immediately if it ‘grabs’ again.
Please note

Never reverse the engine if you’re anchored by a line around the prop. It will only pull the mooring or lobster pot in tighter or lift it.




IF YOU ARE UNLUCKY

If all of the above fails you need to turn off the engine and cut the offending article off the propeller.
This will be a challenging undertaking depending on the conditions, the type of stern the vessel has, and how deep and accessible the propeller is.

Suffice to say the standard approach is for the brave-hearted to don the wetsuit, dive mask and snorkel, or scuba diving gear if trained. Then after fastening on a safety harness or tieing a line around your waist, dive in with a sharp knife on a lanyard, and have a go at it. With thousands of individual plastic strings to cut away off Casablanca Harbour, we got a lot of experience of this.

What we discovered was getting beneath any stern that is bashing up and down in the waves with snorkelling gear and a sharp knife in hand is a second incident waiting to happen. Add to this the water which was cool for us, but may be extremely cold in other situations, plus the current and the fending off of the rise and fall of the vessel, we were exhausted very quickly. Progress was slow, laborious and dangerous.

A serrated knife whipped tightly to a pole allows access from a dinghy
Photo: Michael Harpur


We quickly found the best approach is to avoid getting in underneath the hull in the first place and keep the knife at a distance. This we achieved by quickly whipping a very sharp knife with a serrated edge onto the end of the boat hook and to try cut the rope away from dinghy level. The 'kitchen devil knife' as shown is broadly accepted as being the best knife for the purpose. We looped a mooring line around the hull which we used to get a grip on the topsides. This is very important as you need to anchor the dinghy in place and have something to brace yourself against to cut. Once this was all in place we cut away at the item from that level in much more comfort and cleared it much more easily.

Using the dinghy transformed the effort but if you have a deep sail drive with a beamy boat this may not be possible. You can reach further by donning a mask and snorkel and semi deflating one of the dinghy tubes to dip into the water. But if you are getting your head under the boat make certain to wear a helmet of some sort. Even if you have managed to find a quiet backwater to perform the operation the wake from a passing boat is enough to lift and drop the stern so hard as to knock you into unconsciousness.

I would always try the dingy approach first but if this simply does not lend itself to the vessel your only option is to resort to the snorkelling gear and a knife. In this case ensure there is a boarding ladder deployed, or some other means to get back onboard. As with using the dinghy approach, help yourself to get a purchase by pulling a mooring line around the hull. With this in place, you can hold on to the boat as it rises up and down, plus use it as a brace for the cutting. Having a weight that you can ditch easily will also help you stop fighting your own buoyancy whilst working. Remember to always have a lifeline for safety. But if you are alone, do not enter the water, call for help instead.

AFTERWARDS

Once the prop has been freed engage gear and apply power carefully. Many times your prop may just cut the line and cause no problem, but it’s possible that the fouling might have damaged the propeller, the stern tube, or the prop shaft bearings. Many lobster pot buoys are secured with polypropylene line with a metal core. When wound tight it can damage a folding prop. Even if it does not have a metal core, polyline can melt around the prop shaft, causing torn shaft seals or vibration.

So be particularly alert for any vibration or water ingress. Then don the snorkelling gear in the next quiet anchorage where you can give it a proper inspection.

With thanks to:
Michael Harpur, Yacht Obsession.
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