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03-07-2017, 12:35 PM
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#1
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Guru
City: Victoria TX
Vessel Name: Bijou
Vessel Model: 2008 Island Packet PY/SP
Join Date: Nov 2012
Posts: 5,290
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Prop nuts
My prop is a little loose, and while getting a bottom job I was going to remove the prop and see if the keyway or key was damaged or if the nut was just loose. Is this a DIY job or am I about to screw something up?
I was going to use an impact to get the jamb nut off. How much do you tighten the main nut going back on?
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03-07-2017, 12:57 PM
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#2
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Guru
City: Fort Myers, FL... Summers in the Great Lakes
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 12,834
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Quote:
Originally Posted by cardude01
My prop is a little loose, and while getting a bottom job I was going to remove the prop and see if the keyway or key was damaged or if the nut was just loose. Is this a DIY job or am I about to screw something up?
I was going to use an impact to get the jamb nut off. How much do you tighten the nut going back on?
Attachment 62467
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It's a DIY job......that doesn't prevent you from screwing it up.
Use 2 wrenches to loosen the jam nut. If the prop is loose, a prop puller shouldn't be necessary. To tighten, a block of wood between the prop blade and the hull. Tighten with a BIG wrench and maybe a cheater bar, no impact wrench.
Ted
__________________
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I'm tired of fast moves, I've got a slow groove, on my mind.....
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03-07-2017, 01:16 PM
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#3
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Veteran Member
City: Little River, SC
Vessel Name: Memory Lane (fiberglass)
Vessel Model: 1974 Pacemaker 40 Flush deck Motor Yacht
Join Date: Jan 2016
Posts: 89
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When you are done; It looks like there is a hole in the shaft for a cotter pin, I would add one, you know, belt and suspenders.
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03-07-2017, 01:36 PM
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#4
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Guru
City: Victoria TX
Vessel Name: Bijou
Vessel Model: 2008 Island Packet PY/SP
Join Date: Nov 2012
Posts: 5,290
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Thanks for the help. Oh yeah there was a cotter pin. I removed it.
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03-07-2017, 01:51 PM
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#5
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Guru
City: Vermont
Join Date: Jan 2013
Posts: 10,092
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Right, definitely no impact wrench. There are a bunch of articles out there on how to correct install a prop. I had a bit of a wobble in my drive line, and it turned out to be due to an incorrectly seated prop. The tape needs to be spotlessly clean. D'Antonio has a good article on his site.
__________________
MVTanglewood.com
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03-07-2017, 02:02 PM
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#7
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Valued Technical Contributor
City: Litchfield, Ct
Join Date: Aug 2012
Posts: 6,784
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If your nut is loose then your prop may have been "riding on the key" which can make the prop vibrate. This is the case when the key pushes forward in the keyway as you put the prop on so that it is the key itself that stops the prop from going forward as the nut is tightened, not the taper fit of the prop to shaft.
Put the prop on without the key and tighten the nut up a bit. Scribe a line where the prop stops on the shaft. Then reassemble with the key. Make sure that the prop stops at the scribed line.
And BTW there is much debate about the order of the big and little nut. Tony Athens, formerly of boatdiesel, believes that the little nut should go on first. See Propeller installation / Big Nut vs. Little Nut - Seaboard Marine for a full discussion of prop assembly.
David
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03-07-2017, 02:02 PM
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#8
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Guru
City: Victoria TX
Vessel Name: Bijou
Vessel Model: 2008 Island Packet PY/SP
Join Date: Nov 2012
Posts: 5,290
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Prop nuts
Ahh. According to that DAntonio article. it appears my prop nuts are installed backwards.
I have a little play in the prop, so I hope the key and keyway are OK. Thanks for that additional info. And it does seem like I have a little more vibration than I used to.
I'm at a DIY yard in the middle of a bunch of shrimp boats so no yacht type experts here.
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03-07-2017, 02:10 PM
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#9
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Guru
City: Ft Pierce
Vessel Name: Sold
Vessel Model: Was an Albin/PSN 40
Join Date: Oct 2011
Posts: 28,146
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Quote:
Originally Posted by cardude01
Hmm. So according to that article. it appears my prop nuts are installed backwards?
I have a little play in the prop, so I hope the key and keyway are OK.
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In reference to the nut order....not according to every expert but one I know of including the US Navy.
Take look at the link I posted.
Engineering principles are that the first nut snugs the prop and the big one tightened behind it actually takes the load as it pushes the thinner nut off its threads a bit. The bigger nut should be carrying the load, not the smaller.
Now if you do things differently, and epoxy the little nut after tightening the big nut, well I can't say that doesn't work, as there often are many different ways to do things and get the same result .(something lost on a few here)
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03-07-2017, 02:16 PM
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#10
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Guru
City: Powell River, BC
Vessel Name: Northern Spy
Vessel Model: Nordic Tug 26
Join Date: Feb 2012
Posts: 4,075
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Here it is again:
The thin nut goes on first…
*
I spent 11 years wrenching on submarines.**When I reflect back, I am still amazed at the amount of useful technical training that the Navy provided me.**One of my favourite technical manuals to this day is NavShipsTechManual*Chapter75, Fasteners.* Use it all the time.
*
To quote:
*
075-5.3.4 JAM NUTS (LOCK NUTS). Jam nuts are an older variation of the prevailing torque concept. They are not usually recommended for new installations due to the tendency to use an improper thickness for the jam nut and to install them in the wrong relative positions.
*
075-5.3.4.1 Jam Nut Assembly. The jam nut assembly requires a regular or main nut and a thin jam nut, as shown in Figure 075-5-5. The assembly is installed with the thinner nut between the thick nut and the bearing surface. The main nut has to be as thick as if no jam nut were being used, because the main nut carries all the working load. The jam nut is usually about 2/3 as thick as the main nut. If the jam nut is too thin, however, the threads in the jam nut area will be damaged as the main nut will pull the bolt threads partially through the jam nut. Conversely, if the jam nut is too thick, the main nut cannot distort the threads enough.
*
075-5.3.4.2 Tightening the Jam Nut. At assembly, first tighten the jam nut to the same or slightly less percentage of the preload torque specified for the main nut, based on the relation the jam nut thickness bears to the thickness of the main nut. Then hold it in position with a wrench while you tighten the main nut. For example, if the jam nut is 2/3 as thick as the nut, tighten the jam nut to 1/2 to 2/3 of the torque used for the main nut. Then, when the main nut is tightened to the preload torque specified for the bolt, it stretches the bolt (stud), thereby tending to pull it through the jam nut. Any vibration or load that tends to loosen the bolted joint will allow the bolt to shrink back to its original length, leaving the jam nut tight against the main nut. This creates the necessary prevailing torque to prevent the jam or main nut assembly from rotating on the bolt.
*
Chapter*75*can be downloaded here:* www.hnsa.org/doc/nstm/ch075.pdf
Regards,
*
Mike Pedersen
NORTHERN SPY, Nordic Tug 26
Powell River, BC
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03-07-2017, 02:42 PM
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#11
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Guru
City: Victoria TX
Vessel Name: Bijou
Vessel Model: 2008 Island Packet PY/SP
Join Date: Nov 2012
Posts: 5,290
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Ok. Thin nut first. I savvy now.
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03-07-2017, 02:59 PM
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#12
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Guru
City: Victoria TX
Vessel Name: Bijou
Vessel Model: 2008 Island Packet PY/SP
Join Date: Nov 2012
Posts: 5,290
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Hey while I'm at it is there something I can put on that prop to make it smooth again? The power washer got off some of the growth but there is still some calcium looking deposits that I would like to get off if I can do it without destroying the propeller.
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03-07-2017, 03:15 PM
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#13
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Guru
City: Powell River, BC
Vessel Name: Northern Spy
Vessel Model: Nordic Tug 26
Join Date: Feb 2012
Posts: 4,075
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Soft, fine grit flapper wheel or a medium scotch brite wheel is what I've used.
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03-07-2017, 03:18 PM
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#14
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Guru
City: Ft Pierce
Vessel Name: Sold
Vessel Model: Was an Albin/PSN 40
Join Date: Oct 2011
Posts: 28,146
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Soft wire wheel in fast drill of grinder...if not soft touch lightly...
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03-07-2017, 03:55 PM
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#15
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Guru
City: Quebec
Vessel Name: Bleuvet
Vessel Model: Custom Built
Join Date: Jan 2016
Posts: 4,375
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Quote:
Originally Posted by cardude01
.. it appears my prop nuts are installed backwards...
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Your prop has nuts? and they are backward?
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03-07-2017, 04:46 PM
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#16
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Guru
City: North Charleston, SC
Join Date: Sep 2010
Posts: 4,870
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If your prop is loose and wobbling, you have a problem. I won't try to describe the process here but the taper of the shaft and the taper of the prop bore are supposed to match perfectly. There's a process using a fine abrasive compound to make this happen. Look it up.
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03-07-2017, 04:59 PM
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#17
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Guru
City: Victoria TX
Vessel Name: Bijou
Vessel Model: 2008 Island Packet PY/SP
Join Date: Nov 2012
Posts: 5,290
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Prop nuts
Quote:
Originally Posted by WesK
If your prop is loose and wobbling, you have a problem. I won't try to describe the process here but the taper of the shaft and the taper of the prop bore are supposed to match perfectly. There's a process using a fine abrasive compound to make this happen. Look it up.
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I would not describe it as loose and wobbling, but there definitely is some play back and forth. Yeah I saw that process described in that DAntonio article PSneed posted. Hopefully I don't need to do all that.
https://youtu.be/2jxX-yS-M7E
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03-07-2017, 05:04 PM
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#18
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Senior Member
City: LAFAYETTE,LA
Vessel Name: Relenti
Vessel Model: Atlantic 30, 1983
Join Date: Mar 2015
Posts: 451
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Quote:
Originally Posted by cardude01
Ahh. According to that DAntonio article. it appears my prop nuts are installed backwards.
I have a little play in the prop, so I hope the key and keyway are OK. Thanks for that additional info. And it does seem like I have a little more vibration than I used to.
I'm at a DIY yard in the middle of a bunch of shrimp boats so no yacht type experts here.
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Thin nut first. No impact wrench. Find one of the shrimpers that is friendly (might cost you a beer or two) and he can enlighten you on the wobbly prop as well as some other things you might want to know. These guys know boats. Haven't done this to a prop on a real boat but laping compound does the trick to seat the prop correctly on my model race boats (up to 30k RPM).
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03-07-2017, 05:08 PM
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#19
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Guru
City: Pender Harbour, BC
Vessel Name: Gwaii Haanas
Vessel Model: Custom Aluminum 52
Join Date: Sep 2013
Posts: 3,791
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First of all, I would put to you that we are all "prop nuts."
Secondly, Northern Spy, you must have been a good swimmer to wrench submarines for 11 years, especially if they were Canadian as I thought ours all sank...?
__________________
Don't believe everything that you think.
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03-07-2017, 05:11 PM
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#20
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Guru
City: Powell River, BC
Vessel Name: Northern Spy
Vessel Model: Nordic Tug 26
Join Date: Feb 2012
Posts: 4,075
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Quote:
Originally Posted by Xsbank
First of all, I would put to you that we are all "prop nuts."
Secondly, Northern Spy, you must have been a good swimmer to wrench submarines for 11 years, especially if they were Canadian as I thought ours all sank...?
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Moved to Canada after I got out of the US Navy in '96. West Ed mall had the bigger fleet then.
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