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Old 12-03-2008, 09:33   #1
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Question Propeller Reinstallation - Torque?

I have a fixed 3-blade prop, 1-3/4in shaft and the prop nuts are 1-15/16in.

How tight should these be? I assume just "tight" against the prop hub and then the jamb nut gets snugged up without excessive torque? I will also be sure that the key does not ride up out of the keyway as I tighten it all.

Thanks in advance
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Old 12-03-2008, 11:20   #2
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Remember, if you have different size nuts put the larger one on the outside jamming it against the smaller one, this way more threads take the load.
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Old 12-03-2008, 11:30   #3
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Mark, not sure you can give it excessive torque. Tighten the first nut as tight as you possibly can, then some. Do the same again with the second.
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Old 12-03-2008, 12:51   #4
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Tighten the first nut as tight as you possibly can, then some.
Ummm, that is rather open to an ooops moment :-) Firm but not over tight is the way. About what you can get out of a shifter large enough to take a nut that size. But don't go swinging any longer pipe off the end. The beauty of a tapered shaft is the taper gives the mating joint a tremendouse amount of load. Place too much load on it and you can strip the nut or crack the prop or deform it.
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Old 12-03-2008, 14:05   #5
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Jam nuts

The second paragraph of the text in the following link addresses this issue, along with the apparent dearth of specific torque information for prop shafts, for example:
The Jam Nut
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Old 13-03-2008, 02:08   #6
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I usually take a wrench that fits the nut and do pull ups on it a few times. Then I 'ring' the prop hub (lightly) with a hammer. This vibrates it further on the taper followed by a few more pull ups. Why am I so weird about it? I had one come loose once! Never want that again.
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Old 13-03-2008, 02:28   #7
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I usually crank a nut till it starts to thread and then back off half a turn. Works good with metal but have broken a few plastic fittings

As Wheels knows. I am not an engineer
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Old 13-03-2008, 05:47   #8
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OK so it sounds like I need to go a bit tighter than I had thought.

So how do you lock the shaft while "doing pull-ups" on the wrench? The old 2x4 between the prop blades? Or is that why there are pipe wrench marks on the shaft just behind the coupling...?
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Old 13-03-2008, 07:48   #9
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2x4's between one of the prop blades and the underside of the hull. Never put a pipe wrench on your shaft. It will mar the shaft, force bits of steel from the wrench into your expensive alloy shaft, and make a place for crevice corrosion to start. If there are marks on your shaft inside, some PO was trying to do something that he probably shouldn't have been doing.

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Old 13-03-2008, 08:09   #10
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Thanks Richard... I knew as much and have already pitched the PO's pipe wrenches off the boat
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Old 13-03-2008, 08:46   #11
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Originally Posted by markpj23 View Post
So how do you lock the shaft while "doing pull-ups" on the wrench? The old 2x4 between the prop blades?
Run a length of 2x4 or 2x2 between the strut and the rudder. Then rotate the prop until it comes into contact with it.
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Old 13-03-2008, 10:58   #12
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Yup...a block of wood between the blades against the hull. Try not to brace against the thinner part of the blades.
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