Propeller making a weird sound

[Jstupot]

Hello, today my partner and me took our recently bought narrow boat out for the first time along the Grand Union near to London. At first there were no problems, but then the propeller seemed to be struggling a bit making regular knocking sounds as if it was continuously hitting something. I thought maybe a plastic bag or weeds had got caught on the prop so pulled up as best I could and checked the weed hatch, everything fine.

The canal did look quite shallow at this point so was the prop just hitting weeds at the bottom or is there a problem?

[Chris-B]

Allow me to connect my crystal ball via bluetooth

[Tonka]

shaft has come out of the coupling and needs knocking back in. The boat name is not Tilly by any chance

[NB Lola]

Possibly the water nymphs using their hammers ?

[Jstupot]

Thanks Tonka for the the useful reply. No it's not Tilly.

Is this a simple problem? I'm assuming we have to go to a boatyard to get it repaired!

[Tonka]

Not if it is as described.Just aft of the gearbox is a coupling with allen keyed grub screws and if you loosen them you can then go into the weed shaft and knock the end of the shaft and hopefully the shaft will move forward. Then re-tighten allen grub screws and weed hatch. I had to buy long reach allen keys to get the screws tight enough to stop it re-occurring. It used to happen a lot when I owned Tilly which is why I asked the name. Hopefully that is the problem

[Arthur Brown]

When my boat's prop made funny noises and slowed to a stop, it had collected a pair of trousers fron the Nottingham Canal by the bend that is where Boots was in Nottingham. It was very obvious and lots of hard work in the water to clear it.

 

What CAN you see?

Is the inboard section of the propshaft free of obstruction? Can you see the whole outboard length or the prop and shaft through the weed hatch?

[Jstupot]

Thanks Tonka. By the way I have passed Tilly somewhere in the area.

Not sure if we are confident enough to do that ourselves, but at least we may have some idea of what we are looking at.

[David Mack]

shaft has come out of the coupling and needs knocking back in. The boat name is not Tilly by any chance

Not impossible, but rather unlikely that is the problem. Are you sure there is nothing caught on the prop or the prop shaft or the rudder?

[matty40s]

Ah, was wondering when this annual question would rear it's head.

 

Congratulations

You are the recepient of the Fallen Leaves Award 2016.

 

As you go along, your prop picks up fallen leaves and they clog up the prop, limiting drive and making the engine strain.

You stop, open the weedhatch, and there's nothing there.....as they have all fallen off and sunk between you stopping and getting the hatch off.

 

When it happens again (frequently at this time of year), take the boat out of gear and give it a quick reverse blast of 1/2 second, then carry on forwards...looking back at the big much of leaves that you have just thrown off.

[Jstupot]

Thanks Arthur. I could see the prop through the weed hatch and there was nothing attached to it.

Thanks Matty. That could make sense as there noticeably more leaves around today all over and in the boat. I hope this is the problem.

[matty40s]

This is undoubtedly the problem, happens every year to new boaters and hirer's.

We get people in asking us to look at their gearboxes, drive plates and all sorts, just because of the blasted leaves.

[nipper]

Just to add to Matty's answer.

 

just be aware of how shallow the water is your cruising in because sticking it in reverse gear and giving the engine a rev, is, on a very shallow canal, a sure way of picking something bigger up on your prop that you have disturbed.

 

My solution to drop off leaves and other crud that gathers in the swim is just to take the engine out of gear, you can then look at the back of the disturbed water and generally see all the leaves and crud dropping away. Doing it this way also has the effect of keeping the boat going along albeit a little slower until you engage forward again!

 

Nipper

[Jstupot]

Thanks everyone. Very reassuring.

[Tony Brooks]

Thanks Arthur. I could see the prop through the weed hatch and there was nothing attached to it.

Thanks Matty. That could make sense as there noticeably more leaves around today all over and in the boat. I hope this is the problem.

 

You really need to feel around the shaft. When you pick up something like in ear earphones they hang down when the shaft is stationary so it looks as if there is nothing there. Fishing weights on a length of line also act in a similar way. Both cause knocking sounds when under way and sometimes only at certain revs.

[Sea Dog]

Whilst you have your arm down the weed hatch, feel the edges of the prop for nicks and dings. It's surprising how much noise and vibration even quite minor prop deformities can cause. Careful though, you could find something sharp.

[ditchcrawler]

Also right at the bottom on the skeg, anything hung on there will suck up to the prop. A friend of mine had a tarp on there and the boat wouldn't go, he called RCR and they couldn't find what was wrong and didn't know about his gearbox, My friend knew that Jono from Braunston would be able to sort the gearboax, he came out and sussed it in minutes.

[Flyboy]

Also right at the bottom on the skeg, anything hung on there will suck up to the prop. A friend of mine had a tarp on there and the boat wouldn't go, he called RCR and they couldn't find what was wrong and didn't know about his gearbox, My friend knew that Jono from Braunston would be able to sort the gearboax, he came out and sussed it in minutes.

Also could be some thing attached to the rudder. I picked up a solid rubber pipe fender on a length of rope around the rudder once & it made a hell of a noise banging the bottom of the counter in the prop wash. When I retrieved it I found it still quite usable.

[cheshire~rose]

 

We picked up "something" on the prop of Python last week. It only made a noise when in reverse. We had entered the last lock of the day and were just a few hundred yards from her mooring with failing light so the helmsman said he would continue and check the hatch when she was moored up.

 

She was in the lock in reverse as I went to work the lock. Standing by the helm you could just hear a muffled thud..... thud.... thud as a base below the far more noisy 2 pot air cooled Lister. As I went to operate the paddles at the front of the lock I could no longer hear the Lister but the thud.... thud... thud was resonating through the hull and made it sound like she had a Bolinder engine

 

A trip down the weed hatch revealed we had picked up a pipe fender, the rope was around the shaft and the fender was rhythmically hitting the bottom of the boat. I am glad it was just the rope in the prop!

[dmr]

 

We picked up "something" on the prop of Python last week. It only made a noise when in reverse. We had entered the last lock of the day and were just a few hundred yards from her mooring with failing light so the helmsman said he would continue and check the hatch when she was moored up.

 

She was in the lock in reverse as I went to work the lock. Standing by the helm you could just hear a muffled thud..... thud.... thud as a base below the far more noisy 2 pot air cooled Lister. As I went to operate the paddles at the front of the lock I could no longer hear the Lister but the thud.... thud... thud was resonating through the hull and made it sound like she had a Bolinder engine

 

A trip down the weed hatch revealed we had picked up a pipe fender, the rope was around the shaft and the fender was rhythmically hitting the bottom of the boat. I am glad it was just the rope in the prop!

 

We got one of them just below Stoke Bruerne and it had wrapped round the skeg. In forward it dragged behind us out of harms way. In reverse it went into the prop and made a right racket, but when I went down the weedhatch it had sunk so there was no sign of it.

 

.............Dave

Just to add to Matty's answer.

 

just be aware of how shallow the water is your cruising in because sticking it in reverse gear and giving the engine a rev, is, on a very shallow canal, a sure way of picking something bigger up on your prop that you have disturbed.

 

 

 

Nipper

 

And hence the half second blast of reverse. It takes no time to throw stuff off the prop but a little while to suck stuff off the bottom so a short blast works fine. Not so easy with a proper trad engine but with the JD3 nifty use of gears and speedwheel will do it fine(plus a lovely plume of black smoke). After the blast wait several seconds before going back into forward in order to let all the crap settle back to the bottom.

 

................Dave