How to tighten a prop nut.

[Graham_Wright]

Update.

Dived yesterday, water 9°. Removed nut and cone spacer. Prop needed to be tapped to pull off. Shaft looks pristine, no scoring.

On the bank, the prop bore shows two bright rings which are smooth and occupy around two thirds of the total length.

I failed to find any lapping paste locally except one which was water based.

Tomorrow, I will coat the inside of the prop bore with valve grinding paste and give it as many turns on the shaft that the water temperature permits. I will then tighten the nut to the maximum I can achieve with the one home made spanner and pin it. The problem foreseen is finding the split pin hole. There is enough thread protruding past the nut to attach a jubilee clip to locate it but working in poor vis will not be fun. Said jubilee clip will prevent using a socket spanner.

 

[rogerthebodger]

. The problem foreseen is finding the split pin hole. There is enough thread protruding past the nut to attach a jubilee clip to locate it but working in poor vis will not be fun. Said jubilee clip will prevent using a socket spanner.

Can you mark the end of the shaft so it will show the orientation of the split pin hole to aid lining up the slots in the nut.

If there is enough thread you could also all a lock nut as well

 

[Graham_Wright]

Can you mark the end of the shaft so it will show the orientation of the split pin hole to aid lining up the slots in the nut.

If there is enough thread you could also all a lock nut as well

Yes I think so. A junior hacksaw would probably do the job.

There has been controversy over the advisability of lock nuts. I thought they did the job until I read a well thought out analysis. What does the lock nut do?

There is interesting information here;- http://www.boltscience.com/pages/twonuts.htm.

I have another nut and will use it - why not?!

 

[Norman_E]

If the prop fits the taper well over 2/3 of its length I don't think you need to lap it, and doing so carries a significant risk as grinding particles can embed in the softer metal of the prop and remain despite cleaning, leading to scoring of the shaft in future.

 

[rogerthebodger]

Yes I think so. A junior hacksaw would probably do the job.

There has been controversy over the advisability of lock nuts. I thought they did the job until I read a well thought out analysis. What does the lock nut do?

There is interesting information here;- http://www.boltscience.com/pages/twonuts.htm.

I have another nut and will use it - why not?!

junior hacksaw was also what I was thinking

I agree locknuts are not the best being only a friction lock unlike a split pin which is a positive lock.

BTW my prop is held on with a left hand threaded nut and a right hand internal thread in the end of the shaft so my locking is left hand against internal screw against the prop nut.

 

[Graham_Wright]

If the prop fits the taper well over 2/3 of its length I don't think you need to lap it, and doing so carries a significant risk as grinding particles can embed in the softer metal of the prop and remain despite cleaning, leading to scoring of the shaft in future.

I agree but scoring could only occur with movement which should not happen anyway.

Anything which reduces my time in the water is very welcome!

I think I will lap, then remove the prop for cleaning of it and the shaft and replace.

 

[Fr J Hackett]

Put the prop on whang it up, put the pin in, go to where you need to be, dry out do the job where you have time, can see what you are doing and make a proper job of it.

 

[Graham_Wright]

It all went smoothly. Prop off, bore loaded with valve grinding paste. Offered onto shaft and rotated a few dozen times. Prop off and cleaned on the bank. Shaft cleaned. Prop replaced. Spacers and nut replaced. Nut tightened with long spanner and nudged round until split pin hole lined up. Pin replaced and splayed.

Reasonably straightforward. Took around half an hour. Biggest problem was adjusting for the changes in buoyancy in line with what I was carrying.

And it was cold!

 

[bikedaft]

Well done ☺ how did you lock the shaft?

 

[Graham_Wright]

Well done ☺ how did you lock the shaft?

I used the gearbox. It did resist strongly and defeated my nut tightening spanner.

 

[Fr J Hackett]

I used the gearbox. It did resist strongly and defeated my nut tightening spanner.

So after all the talk about torque see what I did there:encouragement: you just changed it up popped the pin in and away you go. Are you going to dry out later and check you work?

 

[bikedaft]

I used the gearbox. It did resist strongly and defeated my nut tightening spanner.

Screwdriver on starter ring to lock engine?

Impressed, doing that in the water

 

[Graham_Wright]

Screwdriver on starter ring to lock engine?

Impressed, doing that in the water

I intended to block the prop against the hull to counter the nut tightening torque. Unfortunately, I left the wooden blocks intended for the purpose in the car. From previous experience (on son's sunken boat recovery) wood floats and there may have been "difficulties".

I believe the nut is probably tight enough and will recheck/further tighten on the hard after her first "passage".

The cold was the determining factor and it took half an hour to stop shivering!