How to get the right prop?

[jennywren]

So, this is the brilliant thing that happened to me today; my propeller fell off. My guess would be the pin holding it on came loose somehow, allowing it to simply unscrew itself and drop off.

Coming out of a lock and realised suddenly I had no drive. Check prop shaft and gearbox coupling because that's what I've had problems with before and have been worrying about. Nope-all fine. Put my hand down weed hatch and tah-dah...propeller gone. As an afterthought, boat did not reverse when I tried to slow into the lock, so suspect I either lost it just before or actually in the lock. I can't imagine there's much hope of fishing it out again-water a good depth and really murky outside lock and can't exactly go fishing in a lock for it, and no idea of more precisely  may have lost it.

Aside from that it is not going to be cheap, I have no idea where to even start with getting the right replacement. The only thing I know is it was a 3 blade one , I don't know what size it was (although I can maybe make a reasonable guess) or what sort of metal it was or what sort of pin was meant to be holding it on. Can't afford to get someone to replace it for me (tbh, I can't actually afford the new prop but since there is no moving without it and I'm stuck half way up the Rochdale canal, affordablity is kind of neither here nor there; and other than ordering the part, the most difficult it gets is just screwing it on and making sure it's secured properly, right?) so would really appreciate any advice about how I go about shopping for propellers.

[rusty69]

Wow, what a bummer. 

 

Would it be worth looking on the cill? 

[jonesthenuke]

IIRC a previous thread on this type of problem had somebody suggesting contacting a local diving club as they may like the challenge of finding it. You never know.

Replacing it will be a challenge as I would think you will need t get boat out of the water. 

 

[nicknorman]

Oh, sounds most unfortunate! To be honest I think it would be worth putting some effort into retrieving it. It is likely to be brass/bronze so unfortunately, not magnetic. It is likely to have come off when in reverse since the prop is being pulled backwards at that point. So backtrack the path the boat took into the lock, try to remember when you put it in reverse, and it will be within a few feet. Prod about with a stick until you feel something hard the right shape. Then you just have to get wet, followed by a long shower!

Typically a prop is held onto the shaft by a taper - ie the internal bore of the prop is tapered, and the external shape of the shaft is tapered so they come together and are squished together when you tighten the nut on the end (which you've also lost, but will be easier to replace). There will be a slot lengthwise in the shaft, and a matching one on the prop internal bore. A "key", which is an oblong piece of metal, goes between these to help lock the parts together in rotation. Finally, the nut will probably be castellated and there will be a radial hole in the end of the threaded portion of the shaft. A split pin goes into this hole to prevent the nut from undoing.

So for a new prop you need to get the following correct:

Diameter. You can measure the distance between the centre of the shaft and the top of the  skeg and bottom of the counter. Use the shorter distance if they are different, subtract perhaps 2" for clearance, and double the figure for the diameter.

pitch: once you know the diameter, there are various calculators on the internet into which you put boat and engine details, prop diameter - and it will work out the pitch

then you need to know the diameter of the shaft

then you need to know the degree of taper on the shaft - if it prop's taper doesn't match with the shaft's taper, the same thing will happen (it will drop off after a while!

When installing the prop you will need to ensure that the key doesn't quite bottom out in the slots, otherwise the taper surfaces will be held apart.

Chances of getting all this right in the water is minimal. Which is why I think you need to bite the bullet and go diving for the prop!

Once you have the original prop, you will just need a key, nut and splitpin (or possibly self-locking nut). Note that the key might have sheared with the bits remaining in the respective slots.

[jennywren]

I think the prop fell off almost certainly in the lock itself (I didn't put it into reverse until I was in the lock)...which I would imagine is not a safe place for anyone to go diving about in? Also not somewhere I can reach to try and find it by poking about.  Though I guess that does narrow it down to that one half of the lock where it's likely to be.

Edited June 13, 2017 by jennywren

[sans allumette]

@jennywren

If you decide to go fishing for it and to get in canal, do please wear stout footware. The first time i had to do that my feet were ripped to shreds with broken glass...

And afterwards shower like there is no tomorrow.

[ditchcrawler]

4 minutes ago, jennywren said:

I think the prop fell off almost certainly in the lock itself (I didn't put it into reverse until I was in the lock)...which I would imagine is not a safe place for anyone to go diving about in? Also not somewhere I can reach to try and find it by poking about.  Though I guess that does narrow it down to that one half of the lock where it's likely to be.

Feel with a boat pole, pull the boat in and lower the lock it will probably be only 4 feet deep, if its a very short pound below then no problem emptying the lock

[Detling]

Try using a fisherman's landing net to explore the bottom of the lock  It won't be strong enough to lift it though. You will need a small boat in the empty lock to search from. If located the lock will be probably be about 4 to 5 feet deep it may be possible to get a diver in a wet suit to duck down and lift it. Best of luck.

 

[nicknorman]

1 minute ago, jennywren said:

I think the prop fell off almost certainly in the lock itself (I didn't put it into reverse until I was in the lock)...which I would imagine is not a safe place for anyone to go diving about in? Also not somewhere I can reach to try and find it. 

If you are sure you didn't put it into reverse until the back of the boat was in the lock, I think this makes it easier. With the lock empty, the depth of water will only be 4 feet or so (you can check with your cabin shaft). You could climb down the ladder and wade about in the lock. The only thing I would say is that you definitely need someone else around to keep watch in case of difficulty and to prevent anyone else operating the lock, throw you a lifering, help to pull you out etc. Depends on your level of fitness / health I suppose. Or at least, you could mandhandle the boat into the empty lock and prod about with a stick, you will have the benefit of a solid brick bottom rather than gloopy soft mud.

If you are in the middle of a flight of locks with a short pound below, you could perhaps consider draining some of the water from the pound/lock if the depth of water is uncomfortably close to your neck.

[john6767]

I don't suppose it is a short pound below that lock, if it is I would be temped to drain it down a "bit".  I was considering that when I lost my glasses on Lapworth but my wife persuaded me not to .

Edit to add, Nick had the same idea!

Edited June 13, 2017 by john6767

[ditchcrawler]

Contact CRT and they may lend you a crome to rake around with 

[jennywren]

29 minutes ago, john6767 said:

I don't suppose it is a short pound below that lock, if it is I would be temped to drain it down a "bit".  I was considering that when I lost my glasses on Lapworth but my wife persuaded me not to .

Edit to add, Nick had the same idea!

It's fairly short...I am tempted.

I can see the consensus is that the best move is to try and fish it out though. I'm 100% sure I could not do it on my own (it's just me-I'm 5'1, I do not have any sort of long pole or fishing net or anything, my boat is now 4 locks up, I don't have access to any small boats) but maybe I can get my brother to come on a wading mission with me at the weekend (and I'll supervise  )

[ditchcrawler]

6 minutes ago, jennywren said:

It's fairly short...I am tempted.

I can see the consensus is that the best move is to try and fish it out though. I'm 100% sure I could not do it on my own (it's just me-I'm 5'1, I do not have any sort of long pole or fishing net or anything, my boat is now 4 locks up, I don't have access to any small boats) but maybe I can get my brother to come on a wading mission with me at the weekend (and I'll supervise  )

As I said, call the local CRT team, tell them whats happened and see if you can borrow the Crome

[Flyboy]

Why not contact the local sub aqua club ?  They are usually quite keen on a challenge in exchange for a few beers.

Edited June 13, 2017 by Flyboy

[36national]

wow what a bottomer.

On the plus side if you didnt go into reverse till you were in the lock thats almost certainly where it is.

You might find the diameter pitch and handedness of your prop on a survey report  if you have one but you need more info than that. Id do all of the above suggestions to try and find it and see which works first.  Thats a load less hassle than trying to spec and obtain a new prop, plus you stand to save a good few quid, plus I reckon you got a pretty good chance. Which lock are you at?

Good luck and the humour of dripping wet shivering brothers approaching the early stages of hypothermia can often be restored by the repeated application of  large brandies to the back of the throat. 

[sharpness]

Covered by insurance?

RCR member?

[MtB]

To answer your original question instead of swerving off at a tangent, if you tell us the length and width of your boat, and which engine you have we can make an educated guess at prop size. 

Or if you are willing to buy a new one, Crowthers will calculate exactly the right blade if you call them. 

http://www.crowthermarine.co.uk/

 

[nicknorman]

1 minute ago, Mike the Boilerman said:

To answer your original question instead of swerving off at a tangent, if you tell us the length and width of your boat, and which engine you have we can make an educated guess at prop size. 

Or if you are willing to buy a new one, Crowthers will calculate exactly the right blade if you call them. 

http://www.crowthermarine.co.uk/

 

No. You can't calculate the diameter without knowing the available clearance. You can't calculate the pitch without knowing the diameter.

[MtB]

On 13/06/2017 at 23:17, nicknorman said:

No. You can't calculate the diameter without knowing the available clearance. You can't calculate the pitch without knowing the diameter.

Knit-picking.

Measuring the depth of the swim from inside the boat address that, roughly.

[nicknorman]

17 minutes ago, Mike the Boilerman said:

Knit-picking.

Measuring the depth of the swim from inside the boat address that, roughly.

I said that in post 4. Anyway, knits are unpleasant ergo knit picking is a good thing.

Edited June 13, 2017 by nicknorman

[David Mack]

Whereabouts on the Rochdale are you? 

Penninesubaqua.org.uk are based in Todmorden.

 

[MtB]

On 13/06/2017 at 23:37, nicknorman said:

I said that in post 4. Anyway, knits are unpleasant ergo knit picking is a good thing.

 

So not so difficult after all to establish the clearance. I've also done it with a tape measure down the weed hatch.

Fundamentally I agree with you finding the old one is worth quite a lot of effort but if the OP is not inclined, there are two approaches. 

1) Tell us the engine and a few details of the boat and someone here will almost certainly have one approaching suitable lying around which will get the boat moving again, possibly even today. Prop specs are very uncritical if you just want to get on with your trip. As long as the prop is small enough actually rotate!

2) Specify it properly and order a new one the exact right size. Crowthers will take a few days to come up with one.

The taper is pretty must standard. 1:1- or 1:12. One is FAR more common than the other so a roughly correct second hand blade will almost certainly fit the shaft. The harder bit will be finding a nut to hold it on and inserting a locking pin. The boat will need docking for this in my opinion, regardless.

[Alan de Enfield]

It is of absolutely no help to the OP, but having 'lost a prop' myself (some years ago)I have made up  small 'prop rescue kit' which could also be used to clear props which cannot be cleared via the weedhatch.

It gives me roughly 5-10 minutes of air (depending on depth, stress and exertion levels)

(Yes - I used to dive as a hobby)

 

 

Edited June 14, 2017 by Alan de Enfield

[Bee]

I have a prop that is for a 1.5 inch shaft, its about 16 inch diameter and right hand rotation, chances are that it will fit, I have a spare key but no nut to fix it on. You need a new nut and a split pin and a handy person to put the whole lot together and cut the key to length. Its possible if the water is not too murky to cobble it all together to get you home. Welcome to borrow it if you can get to Ironbridge or somewhere near. We are on holiday from the weekend so get in touch soon if it helps.

[jennywren]

All the good ideas have giving me the confidence to I have a go at a few options to try and fish prop out (will give local diving club a try, if no luck there thinking purchasing an inflatable dinghy and something to poke about with would do the trick at least to locate it). Having thought over my entrance to the lock and attempt to slow down, I can narrow down where it will be to a quarter of the lock so it's not a massive area to search over so fingers crossed will get lucky.

Will let you know how I get on...