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Replacement propeller


B2019

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48 minutes ago, B2019 said:

Many thanks Bee. I saw someone taking out the shaft on YouTube and I reckon I can but I spoke to engineer today and they said it was a bit risky to take shaft out in water but might be the quickest and beat bet. 

if you are in shallow water the boat ain't going to sink.   If it has a watertight bulkhead between the engine space and the cabin then the potential for any internal flooding will be limited.

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New information. 

 

I tried two bolts today and a one inch nut is too big so I'm going to try a 0.9 inch (22mm) nut tomorrow. 

 

I also made some clay casts today which are very accurate. Is it me or is 4 inches on the outside small for a drive shaft? 

 

Lock key length is 50mm. 

 

There is no lock hole on the drive shaft thread?? 

 

 

 

IMG_20190526_170030996.jpg

IMG_20190526_154601957.jpg

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6 minutes ago, Mike the Boilerman said:

 

I’m now wondering if your propeller is in the cut, just behind your boat. 

 

 

When I last moved it, the propeller got stuck in weeds as low water, I then stopped, moored the boat up, removed weeds and propeller was still there when I left. Gone a few days later. I got in the river and searched the river around my boat and in a 15 metre radius. Nothing was found.  A propeller can't just disappear by wind!!

6 minutes ago, Mike the Boilerman said:

 

 

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4 minutes ago, Mike the Boilerman said:

 

I’m now wondering if your propeller is in the cut, just behind your boat. 

 

 

I had that happen in the wilds of the Scottish West Coast - came up to a slipway (Sea-Boat), put it into reverse to stop. We slowed down but not a much as we should.

Winched the boat onto its trailer and noticed we were 'propless'.

 

Shoes and socks off and plodged about at the end of the slipway and fortunately found it, managed to pick up a replacement nut at an engineering place.

 

Hadn't put the split pin back in and it unscrewed itself.

 

Spare prop and spare nut purchased at 1st opportunity.

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On ‎25‎/‎05‎/‎2019 at 19:48, Bee said:

What I would do. (and have done)  See if you can draw the shaft out. Can you lift the rudder out of its cup at the bottom? do so and shove it sideways. Does it unbolt from the tiller just under the counter? Is it possible to pull the shaft OUT?  lift the engine and pull the shaft IN? If you can get the shaft out and bung a piece of tapered wood in the stern gland then you can take the shaft to a good industrial fixings supplier, find a nut,  fit a key (carefully, it might be TOO HIGH and prevent the prop fitting properly on the taper and need filing down),  (My present boat has a Whitworth thread on a second hand shaft) Fit the propeller, tighten it all down, drill the nut and shaft and put a good STAINLESS steel splitpin in it. Refit it underwater with prop attached or unfitted if you cant get it past the rudder, re- assemble till the splitpin aligns and the job is done. Wedge the bung in place with a bit of wood rammed up against something solid to stop it popping in and sinking the boat. To find a propeller look in E Bay or ring round boatyards and Midland Chandlers, they sometimes have second hand ones. I've got a suitable one but its right hand. Good luck

 

44 minutes ago, B2019 said:

Spoken to propeller makers today. Best thing to do is take shaft out and plug hole. Send shaft to them. Job done?

 

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like it or not, narrowboats are basically utilitarian designs ........  it seems madness that the prop shaft and the rudder are on the same centreline.

in my book the design would be so much better if the prop shaft was set to one side.

this used to be quite a common arrangement in seagoing fishing boats that had been converted from sail to power, so that the bored hole for the prop shaft did not compromise the strength of the keel and sternpost.

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On 26/05/2019 at 17:10, B2019 said:

New information. 

 

I tried two bolts today and a one inch nut is too big so I'm going to try a 0.9 inch (22mm) nut tomorrow. 

 

I also made some clay casts today which are very accurate. Is it me or is 4 inches on the outside small for a drive shaft? 

 

Lock key length is 50mm. 

 

There is no lock hole on the drive shaft thread?? 

 

 

 

IMG_20190526_170030996.jpg

IMG_20190526_154601957.jpg

is it only me who thinks that looks like dog poo - or perhaps a rather nasty clay model of a gentleman's private part ?

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1 minute ago, Murflynn said:

is it only me who thinks that looks like dog poo - or perhaps a rather nasty clay model of a gentleman's private part ?

Yup. All the rest of us have pure minds...

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On 26/05/2019 at 17:10, B2019 said:

(snip)

I tried two bolts today and a one inch nut is too big so I'm going to try a 0.9 inch (22mm) nut tomorrow. 

(snip)

It's no use just trying random nuts. The thread will have to be measured. The outside diameter will give a clue as to whether it's metric or imperial, and counting the threads on a measured length will give the pitch. (Imperial is defined by threads per inch, while metric is defined by pitch, i.e. distance between thread crests) If metric, it's usually simple: looking up the diameter in thread tables will give an easily checked thread pitch. Imperial can be more complicated, especially if it comes to a choice between UNC and BSW, which will have the same number of threads per inch, but a different thread form.

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3 hours ago, Iain_S said:

It's no use just trying random nuts. The thread will have to be measured. The outside diameter will give a clue as to whether it's metric or imperial, and counting the threads on a measured length will give the pitch. (Imperial is defined by threads per inch, while metric is defined by pitch, i.e. distance between thread crests) If metric, it's usually simple: looking up the diameter in thread tables will give an easily checked thread pitch. Imperial can be more complicated, especially if it comes to a choice between UNC and BSW, which will have the same number of threads per inch, but a different thread form.

and although BSW and UNC seem to be interchangeable in small sizes (say up to about 3/8" diameter) they are definitely NOT in prop shaft sizes.

 

The so called nuts shown in teh phoo. one looks as if its a pipe fitting so a shaft is very unlikely to be thraeded BSP while the other seems to be off an older design of master switch and those threads are so fine I have no idea what they are, possibly a special.

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Some thread pitch gauges will help make the identification simpler. Examples. The ones linked to is all the common, including whitworth and UNC and some of the more uncommon too.

For measuring prop diameter and taper you need something like a vernier caliper and know how to use it to get the accuracy needed. This will work under water, provided you clean and dry it carefully after. There are digital versions too, which are much easier to use, but not waterproof.

 

Jen

.

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A thread file or thread chaser is a very useful tool and cheap. It is a square bar with four different threads on each end, metric or  imperial. Ideal for touching up a damaged thread start to get the nut started. Also by trialing the bar threads on the thread in question at the right angle, hold up to the light or with a torch behind it you can find the correct one before cleaning up a thread. Saved my bacon many times when I've inadvertantly whacked a vehicles driveshaft thread.

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10 hours ago, Iain_S said:

It's no use just trying random nuts. The thread will have to be measured. The outside diameter will give a clue as to whether it's metric or imperial, and counting the threads on a measured length will give the pitch. (Imperial is defined by threads per inch, while metric is defined by pitch, i.e. distance between thread crests) If metric, it's usually simple: looking up the diameter in thread tables will give an easily checked thread pitch. Imperial can be more complicated, especially if it comes to a choice between UNC and BSW, which will have the same number of threads per inch, but a different thread form.

One "nut" is a backnut for plumbing brassware, it will be BSP thread, the other is an electrical conduit nut, the thread on the shaft will be neither of these. Most will be Whitworth, unified course or metric depending on the age.

I would say that you seem to have very limited engineering knowledge and are struggling. Go get professional help now, you will have to in the end.

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