Disaster

[Dutch]

Well we finally got to take our boat out,2 years old so in good condition.Started from Stourport one night in Kinver then onto the Waterfront one night here then on to the Black country museum got to the locks just before there and got what i thought was a foul up round the prop.Opened the hatch and there on the floor was 4 sheared bolts from the coupling,further inspection and found the shaft bent badley,now under tow to Alvechurch for repair.Any ideas what could cause such damage?

[andywatson]

Well we finally got to take our boat out,2 years old so in good condition.Started from Stourport one night in Kinver then onto the Waterfront one night here then on to the Black country museum got to the locks just before there and got what i thought was a foul up round the prop.Opened the hatch and there on the floor was 4 sheared bolts from the coupling,further inspection and found the shaft bent badley,now under tow to Alvechurch for repair.Any ideas what could cause such damage?

 

My money is on a catastrophic prop foul under power.

 

When the prop fouled and stopped turning the engine would try to wind itself around the prop instead of vice versa. The resultant torque has caused the flange bolts to shear. Probably they did not fail simultaneously resulting in the momentary transverse load, sideways movement and hence bent shaft.

 

Try an insurance claim. This is unlikely to be premature wear or bad maintenance.

Edited March 23, 2008 by andywatson

[Malarky]

Sounds like you drifted into a scafold bar or something with a good amount of revs going! How's the prop, and engine mountings bearing up?

[steelaway]

Well we finally got to take our boat out,2 years old so in good condition.Started from Stourport one night in Kinver then onto the Waterfront one night here then on to the Black country museum got to the locks just before there and got what i thought was a foul up round the prop.Opened the hatch and there on the floor was 4 sheared bolts from the coupling,further inspection and found the shaft bent badley,now under tow to Alvechurch for repair.Any ideas what could cause such damage?

 

 

Hi There

 

My intial thought was that the shaft had siezed in the bearing - no gease?

Then maybe the bolts had become loose in the coupling until the coupling was thrashing around and sheared them.

I would expect you would have some audible warning that some thing was amiss with either of these.

What engine/gearbox do you have? A modern gearbox tends to slip with a serius prop foul before any damage is caused.

 

Alex

[blackrose]

It could just be that the bolts were loose before you started and then sheared. I've heard of this happening.

[Dutch]

Looks like the nylock nuts were loose,no auaible warning at all just engine slow down and the no drive

Mick

[Dylan]

Very bad luck . I agree that an insurance claim could be worth a try. Hard to say without seeing the damage first hand, but Blackrose's theory is a strong possibility, or as others have said, a catastrophic prop foul/something seized.

[Dutch]

Looks likie Blackrose was right,the bolts were loose and just sheared,looking at them can see where they have worn and finally snapped

Mick

[andywatson]

Looks likie Blackrose was right,the bolts were loose and just sheared,looking at them can see where they have worn and finally snapped

Mick

 

I check my bolts about twice a year but I'll increase the frequency now.

 

At least this thread will serve as a warning and may save someone else an expensive event.

(-Thus making proper use of the forum.)

Edited March 23, 2008 by andywatson

[Dylan]

I check my bolts about twice a year but I'll increase the frequency now.

 

At least this thread will serve as a warning and may save someone else an expensive event.

(-Thus making proper use of the forum.)

I keep a set of suitable spanners alongside the engine, which are correct for checking the engine mounts and the drive coupling bolts (R&D on mine). That way they are readily to hand, and there is little excuse for procrastination. I have been surprised at the number of times that I have needed to tighten the engine mounts, but not so much the nylocs on the R&D.

[andywatson]

Looks likie Blackrose was right,the bolts were loose and just sheared,looking at them can see where they have worn and finally snapped

Mick

 

I check my bolts about twice a year but I'll increase the frequency now.

 

At least this thread will serve as a warning and may save someone else an expensive event.

-Thus making good use of the forum.

[magnetman]

Its worth using high tensile socket cap bolts and 'binks' locking nuts. They won't come loose like nylocs can, but you will have to use a nut splitter or shear the bolts if you do need to uncouple the drive.

[magnetman]

Sorry that should be BINX not binks.

[Malarky]

I keep a set of suitable spanners alongside the engine, which are correct for checking the engine mounts and the drive coupling bolts (R&D on mine). That way they are readily to hand, and there is little excuse for procrastination. I have been surprised at the number of times that I have needed to tighten the engine mounts, but not so much the nylocs on the R&D.

 

Yeh, engine mounts these days do seem a bit slack at holding their bolts tight. Could it be more sensible if they were mounted leaning towards the engine, so that it "wedges" into them. I suppose this needs to be taken on by builders and engine manufacturers.

[Farey]

Well we finally got to take our boat out,2 years old so in good condition.Started from Stourport one night in Kinver then onto the Waterfront one night here then on to the Black country museum got to the locks just before there and got what i thought was a foul up round the prop.Opened the hatch and there on the floor was 4 sheared bolts from the coupling,further inspection and found the shaft bent badley,now under tow to Alvechurch for repair.Any ideas what could cause such damage?

 

The same thing happened to me last year on the Upper Thames. I was going upstream quite nicely, then went into reverse to stop for the night, and got a horrible noise. 3 bolts had sheared, and then the prop tried to rotate around the axis of the remaining bolt, shearing the two rear engine mountings and bending the prop shaft. I discussed it with the builder (Piper boats) and the engineer who fixed it, and they both thought a log must have got sucked in jamming the prop. I was able to claim for it on the insurance as accidental damage (the boat was also only 2 years old).

 

Chris Farey

[Liam]

I was chugging along a few years ago on the boat when an almighty bang came from under the boat near the weed hatch. A log of about 6 inches diameter got sucked into the prop, between two blades and up into the weed hatch. It stopped the engine dead and I had to spend about an hour trying to bash it backwards with my mooring hammer. It eventually came loose and I was surprised to see about a inch deep gash along the log.

 

Thank god no damage was done to the engine bearers, the shaft, or gearbox but I did notice on the last blacking session that there's a little nip out of one corner of a blade. I think I was pretty lucky to get away with it.

[blackrose]

I hope this isn't a stupid question, but how does one stop the propshaft from rotating when trying to check or tighten the bolts? I put it in gear, but of course with a hydraulic box this doesn't do anything...

 

The nuts all seem tight but there's one that is turning the bolt on the other side. Trying to hold a socket on the nut and a spanner on the bolt on the other side while the prop shaft turns is too difficult for me.

 

Some of the nuts won't take a socket or ring spanner because they're too close to the coupling which isn't great design, and I was also wondering if longer bolts were used, how would a nut and another locknut on top compare to using nyloc nuts?

Edited March 26, 2008 by blackrose

[Mick_B]

I hope this isn't a stupid question, but how does one stop the propshaft from rotating when trying to check or tighten the bolts? I put it in gear, but of course with a hydraulic box this doesn't do anything...

 

The nuts all seem tight but there's one that is turning the bolt on the other side. Trying to hold a socket on the nut and a spanner on the bolt on the other side while the prop shaft turns is too difficult for me.

 

Some of the nuts won't take a socket or ring spanner because they're too close to the coupling which isn't great design, and I was also wondering if longer bolts were used, how would a nut and another locknut on top compare to using nyloc nuts?

Hi Mike

 

If the nuts are that close to the coupling you could try inserting the blade of a large flat screwdriver between the flat of the nut and the coupling. This will stop the nut turning. An open end spanner on the nut, and let it turn until it jams against the coupling should also do the job.

 

If there's a recurring problem with nuts coming loose, what about using castlated nuts and drilling a hole for a split pin as used on ball joints etc?

[blackrose]

Hi Mike

 

If the nuts are that close to the coupling you could try inserting the blade of a large flat screwdriver between the flat of the nut and the coupling. This will stop the nut turning. An open end spanner on the nut, and let it turn until it jams against the coupling should also do the job.

 

If there's a recurring problem with nuts coming loose, what about using castlated nuts and drilling a hole for a split pin as used on ball joints etc?

 

Thanks. Obviously if some people are having problems with nyloc nuts then there must be a better way.

[tomsk]

Thanks. Obviously if some people are having problems with nyloc nuts then there must be a better way.

 

 

Castration?

[Mick_B]

Castration?

[Farey]

Thanks. Obviously if some people are having problems with nyloc nuts then there must be a better way.

 

When I had my boat repaired the engineer recommended fitting an Aquadrive.

 

Chris Farey

[magnetman]

Locking nuts other than those with nylon inserts are available and can be advantageous in some situation, including the avoidance of castration. Another thing is to incorporate a weakest link in the form of a shear bolt so when the block of wood gets wedged by the prop and the engine is a bit of a beast it won't bend anything just shear a bolt instead.Locking nuts other than those with nylon inserts are available and can be advantageous in some situation, including the avoidance of castration. Another thing is to incorporate a weakest link in the form of a shear bolt so when the block of wood gets wedged by the prop and the engine is a bit of a beast it won't bend anything just shear a bolt instead.

[blackrose]

Locking nuts other than those with nylon inserts are available and can be advantageous in some situation, including the avoidance of castration. Another thing is to incorporate a weakest link in the form of a shear bolt so when the block of wood gets wedged by the prop and the engine is a bit of a beast it won't bend anything just shear a bolt instead.Locking nuts other than those with nylon inserts are available and can be advantageous in some situation, including the avoidance of castration. Another thing is to incorporate a weakest link in the form of a shear bolt so when the block of wood gets wedged by the prop and the engine is a bit of a beast it won't bend anything just shear a bolt instead.

 

We heard you twice the first time!

 

You say a shear bolt but wouldn't you need all (4) bolts to be shear bolts for this to work?

[NB Alnwick]

You say a shear bolt but wouldn't you need all (4) bolts to be shear bolts for this to work?

 

Magnetman may have meant a 'shear-pin' - where the connection between drive-shaft and propshaft is in the form of a sleeve over shaft coupling connected by a single pin usually made of a softer metal like brass and held in place by nuts or clips.