Prop nut torque?

[Mudhook]

Just about to refit my prop. Taper is 1:12 on a 25mm shaft; thread is about 20mm OD and 11tpi. Any suggestions as to tightening torque?

Regards, Mudhook

 

[lydiamight]

I think that the most important thing is to make sure that the prop nut and shaft are drilled so that you can put a split pin right through the nut to make sure that it stays in place. Another method is to use a "tab washer" where you can bend the ears of the washer over onto the flats of the prop nut.
As long as the prop nut is reasonably tight you will be OK it you do either of the above---or both if you really are paranoid about the prop falling off.

 

[Tranona]

No need to torque it. The prop will only go up to the top of the taper. Just tighten it up with a ring spanner until it goes no further and the put in the pin or the tab. Obviously you have to stop the prop from turning and a block of wood between the blade and the hull is effective. You might have to back off the nut a bit to line up the hole for the pin.

 

[santelmo]

I have got the same problem and I am paranoid about loosing the prop. I have considered the slit pin but I have a 40mm shaft on a nauticat motorsailor and I dont fancy drilling through that lot and I am not sure where I would get such a long pin from. I think that I would prefere the tab washer solution perhaps a washer made up with an internal tab that fits into the keyway or one with 2 ears one that sits on a prepared flat on the prop and the other on the nut but what material for the washer ss, steel or copper would be easy to work

 

[alan006]

I would definitely go for the folding washer rather than the split pin system. The pin system is fine for the first time but next time you take the prop of and refit it it is either too tight or too loose.

 

[emnick]

should you use 'locktight' as well?

 

[wotayottie]

In my experience, my problem with props isnt keeping them on but getting them off again. So make sure you put something like coppaslip on the taper. The split pin and nut will hold the prop as long as the prop isnt rattling up and down the taper.

 

[alan006]

No, locktight is not recommended. THe best thing I know of is Coppaslip (as per wotayottie).

 

[rob2]

IIRC the old way was to tighten up to whatever torque was given - although I believe a robust hand tight should do - and then increase pressure until the split pin hole was aligned. In practice, if the alignment was poor, it was better to adjust the thickness of the washer until a healthy nip would make the alignment.
I also have experience only of difficulty in removing a prop. I bent and destroyed two pullers one weekend - left it soaked in WD40 and pulled it off by hand three days later!
Rob.