Rope caught up in prop, what maintenance checks to perform?

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Padge01

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Hello,

I'd appreciate some advice following an recent snag whilst sailing in my Wing 25. A Mooring rope slipped of the bow, trailed along the edge of the boat and into the prop which is fitted with a rope cutter.

I only spotted the somewhat shorter mooring rope on the bow towards the end of the sail but i'm certain the snag occurred just after setting off when I noticed a drop of about 50 revs from the engine and a very slight change in the mechanical noise from the propshaft, sounded a bit rumblier along with a bit of a whine.

Other than that the boat felt fine, felt like i had actually gotten away with it. I did go straight home, shut myself in a room and blubbered inconsolably for letting it happen in the first place.

Engine is a Yanmar 1GM10 and the rope was cut cleanly.

What checks would you perform after an event like this? Would you replace any components.
 
Happened to me, although I don’t have a rope cutter fitted. My 1GM10 was purring along nicely at close to max revs when it stopped suddenly with a loud bang. A length, of what turned out to be Kevlar reinforced rope, was wrapped around the prop. I eventually managed to unwind it and get going again, but was plagued the rest of the season with water ingress and vibration.
Turned out the stern tube had become loose so water was coming in between it and the hull. The vibration was because 2 out of the 4 engine mounts had de-bonded when the rope stopped the engine so suddenly.
 
Padge01 said:
Hello,

I'd appreciate some advice following an recent snag whilst sailing in my Wing 25. A Mooring rope slipped of the bow, trailed along the edge of the boat and into the prop which is fitted with a rope cutter.

I only spotted the somewhat shorter mooring rope on the bow towards the end of the sail but i'm certain the snag occurred just after setting off when I noticed a drop of about 50 revs from the engine and a very slight change in the mechanical noise from the propshaft, sounded a bit rumblier along with a bit of a whine.

Other than that the boat felt fine, felt like i had actually gotten away with it. I did go straight home, shut myself in a room and blubbered inconsolably for letting it happen in the first place.

Engine is a Yanmar 1GM10 and the rope was cut cleanly.

What checks would you perform after an event like this? Would you replace any components.
Click to expand...

What rope cutter do you have? My experience with an Ambassador Stripper is that residue from the rope gets jammed between the blades causing friction which could explain the drop in revs. A strip down was required to clear it.
 
Bit late now, but I sail single handed & cannot see the bow lines from the helm very easily once rigged when entering a port. For that reason I have them at a length that just does not quite reach the prop if they do get washed off the deck. My midship lines are easy to see & i always lead these back to the cockpit once one end is looped on to the cleats each side. My stern line is a floating poy propylene.
 
Assume you do not have any "P" brackets as a yacht.
However if anybody has a motor boat with brackets a quick heads up.
Few years ago a rope substantial enough to stall a 130 HP 6 cylinder diesel went round the prop.
Managed to manually uncoil rope by way of a spanner on the bolts on the flexable gearbox/shaft coupling.
No obvious ill affects ie vibration etc.
Slipped the boat the following year and just happened to glance at stern gear, the "P" bracket was about 2" off true.
As emergency repair inserted a small glass fibre wedge between hull and base of bracket to compensate.
Got some eye watering prices for a replacement.
End of season.
Removed bracket, took it round to our local prop shop (INVICTA MARINE) in Chatham dockyard who persuaded it back into shape with the help of some magic and a 50 ton press.
 
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A good few years ago, someone here suggested that the right length for bow lines is just too short to reach the prop from the bow cleat. It's advice I've followed religiously, so I let a stern line drop in backing off a scrubbing grid...

That damaged the rubber doughnut in my flexible coupling. Another thing to check after a serious CLUNK - silence is the engine mounts. If you have a P bracket, that could use a check, too, as could the shaft, which could get bent.
 
I would suggest you check your engine alignment.

I snagged a pot line some years ago and stalled a 100 hp Yanmar at about 3/4 throttle. That deformed the engine mounts, misaligning the engine, and damaged the drive plate between engine and gearbox. All in all it cost about £5k to rectify. I was pretty disappointed that a premium product such as Yanmar was unable to survive such a stall without damage.

I subsequently fitted an Ambassador rope cutter, although that failed to deal with some floating net a few years later, albeit without serious damage on that occasion.
 
On a maiden voyage with a new 1GM10 I caught a floating polypropylene net around the prop that stalled the engine. Got a tow back into port and cut off the offending net and all was well with no damage. That is with a conventional stern tube and no P bracket so you might be lucky and get away with no damage.
Following incorrect advice I had used the standard 20mm coupling on a 3/4" shaft and it is possible that the coupling slipped and lessened the shock. Does anyone make an equivalent to the rubber bush on an outboard propeller that slips to prevent damage when overloaded?
 
We have a whole series of spinnaker sheets of differing lengths but all too short. The normal way that we make these is to wait for a drifting day and when it becomes impossible to sail any more, start the engine and motor over the trailing sheets. Sometimes a bit of a clunk, but generally just two sheets from one!

Never had any damage and the rope cutter (Ambassador) silently does its job. So unless you can detect any vibration or change in engine noise, I would tend to ignore it until you can next dive on the boat or are dried out to check everything. I doubt that you have done any damage and you just need to find a use for some shorter mooring lines.
 
Sounds like your encounter was of the less impactfull variety. Ropes getting caught up free flow can be relatively easy to cut off with a cutter by easing the engine into and out of gear- so as not to form a solid obstruction to the prop. Most lines will othetwise quickly ball and fuse under pressure.

A foul when under power is quickly self righting as in your case, or, brings the whole gear train to a very sudden stop. The latter is when engine mounts and alignment are most likely to suffer.

What to do? If you can see no obvious deformation and there is no significant vibration, no water ingress, you can count yourself lucky. On haulout you will want to check it all out carefully. Feel lucky only a short length of lighter line engaged with the prop in your case, so did not have the length to form a more damaging wrap.

PWG
 
Thanks all. For sure I've been very fortunate on this occasion given the tales of woe among the responses. Had to wince at a few of them, yikes.

The prop is fitted with a Prop-protector so credit to those guys for such a simple bit of kit that appears to have save the day.

I'll take your advice and check engine alignment and suggestion to dive below to check if there is anything fouling the prop, i can already feel the cold. I have an old waterproof camera which i'll take that with me, if there is anything of interest I'll let you chaps know.

Ta.
 
A few years ago I picked up 23 meters of nylon fishing line which stopped the engine. I was told to check that the prop shaft was not bent.
Our local marine engineer was in our yard, and I asked him to have a look for me. He hand clamped a short length of wood to the P bracket and had it just touching the tip of one of the prop blades, then he rotated the prop by hand until the other blade touched the wood.
I thought it seemed a bit of a crude method but I have had no problems.
 
Padge01 said:
I'll take your ... suggestion to dive below to check if there is anything fouling the prop, i can already feel the cold.
Click to expand...
If you're based in the Solent, you could dry out at Hardway for a tenner. I know there are other places, and probably localones wherever you are. Unless you're well equipped, diving in January temperatures isn't healthy. If you're one of those hardy souls who think a dip on New Year's Day is bracing, you'll be fine, but you wouldn't have made the comment about feeling the cold, then ;)
 
Agreed, thanks for helping me think that one through properly.

My boat is located up north, a dip would probably shift my vocal range a few octaves so i've taken your advice and arranged with a local boat yard. Cheers.
 
I collected some three strand blue polypropylene. The sort of stuff you see as tumbleweed in industrial estates and in skips.

The prop had come to a stop . On investigation , the rope had literally melted, and was welded inside the bearing.
Might be worth a check in addition to the others suggested.
 
Another it depends" opinion from me i'm afraid. I worked for 18 years as a marine engineer and have seen all from absolutely no damage, to an engine literally on it's side in the engine bay with a blown out flywheel housing (that one let in a lot of water...)

The only decent answer an honest marine engineer will give you is to haul the boat (most yards will do a deal for a lunchtime or overnight (last one out, first one in lift) or dry her on the rid and check the shaft, p-bracket (if fitted), cutlass bearing, prop, cutter and anode are OK - not bent, damaged, moved or otherwise.

Then, as others have said above, a good check of the engine mounts and alignment check of the engine/shaft would be the 100% method.

The above said, I am not above recognising that this is a lot to ask, and potentially very expensive. I have known many just to carry on regardless and keep a careful eye out for any leakage from the stern seal, a mindful feel for any new vibration, a check that she still reaches max rpm and hull speed and doesn't make any new or unusual noises.

Good luck :-)
 
The event of a biggish diesel engine with a heavy flywheel brought abruptly to a stop while merrily running is frightening, as some above posts attest.
With all the flotsam increasingly found at sea I wonder why it is not standard practice to insert a "mechanical fuse" in the shaft line. Shear pins are common in outboard prop coupling. The bolts in the coupling between gearcase and shaft might be replaced with aluminium ones?
Apart from having to keep spare bolts, which drawbacks could arise?

Sandro
 
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