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12-03-2008, 08:33
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#1
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Registered User
Join Date: Nov 2005
Location: Bradenton FL
Boat: Med Yachts 62 Trawler
Posts: 1,180
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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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Mark
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12-03-2008, 10:20
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#2
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Registered User
Join Date: Feb 2006
Location: nyc/chesapeake
Boat: gozzard 44
Posts: 320
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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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12-03-2008, 10:30
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#3
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Registered User
Join Date: Mar 2003
Location: Wherever the boat is!
Boat: Marine Trader 34DC
Posts: 4,619
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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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12-03-2008, 11:51
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#4
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Senior Cruiser
Join Date: Dec 2003
Location: Marlborough Sounds. New Zealand
Boat: Hartley Tahitian 45ft. Leisure Lady
Posts: 8,038
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Quote:
Tighten the first nut as tight as you possibly can, then some.
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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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Wheels
For God so loved the world..........He didn't send a committee.
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12-03-2008, 13:05
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#5
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Registered User
Join Date: Jan 2005
Location: Seattle area (Bremerton)
Boat: C&C Landfall 39 center cockpit "Anahita"
Posts: 1,077
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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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"I don't think there'll be a return journey Mr. Frodo". Samwise Gamgee
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13-03-2008, 01:08
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#6
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Registered User
Join Date: Nov 2006
Location: Back in Northern California working on the Ranch
Boat: Pearson 365 Sloop and 9' Fatty Knees.
Posts: 10,466
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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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"Life is not a journey to the grave with the intention of arriving safely in a pretty and well-preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming: Wow - what a ride!"
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13-03-2008, 01:28
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#7
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Registered User
Join Date: Jul 2005
Location: new zealand
Boat: Lotus 10.6
Posts: 1,270
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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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"Very well, you hand it over and we'll put your town to our rudder and ne'er return" Captain Barbossa, Black Pearl, Pirates of the Caribbean.
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13-03-2008, 04:47
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#8
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Registered User
Join Date: Nov 2005
Location: Bradenton FL
Boat: Med Yachts 62 Trawler
Posts: 1,180
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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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Mark
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13-03-2008, 06:48
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#9
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Registered User
Join Date: Jul 2006
Location: Florida
Boat: 36 gulfstar
Posts: 68
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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.
Richard
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13-03-2008, 07:09
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#10
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Registered User
Join Date: Nov 2005
Location: Bradenton FL
Boat: Med Yachts 62 Trawler
Posts: 1,180
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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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Mark
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13-03-2008, 07:46
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#11
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Hull Diver
Join Date: Oct 2006
Location: Under a boat, in a marina, in the San Francisco Bay
Posts: 5,427
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Quote:
Originally Posted by markpj23
So how do you lock the shaft while "doing pull-ups" on the wrench? The old 2x4 between the prop blades?
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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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13-03-2008, 09:58
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#12
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Registered User
Join Date: Nov 2006
Location: Back in Northern California working on the Ranch
Boat: Pearson 365 Sloop and 9' Fatty Knees.
Posts: 10,466
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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.
__________________
"Life is not a journey to the grave with the intention of arriving safely in a pretty and well-preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming: Wow - what a ride!"
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