Reply
 
Thread Tools Display Modes
 
Old 12-24-2010, 11:18 AM   #1
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,723
Propeller shaft prep for prop

On inboard boats I usually put the prop on after cleaning the ID of the prop and the taper of the shaft w acetone. Some say to use never-seize. I did that once and the prop DID come off quite easily. I worry though if the prop, through torsional vibration work (move back and forth) a tiny bit and wear the propeller bore. What do the rest of you do?
__________________
Advertisement

Nomad Willy is offline   Reply With Quote
Old 12-24-2010, 01:17 PM   #2
TF Site Team
 
Larry M's Avatar
 
City: JAX, FL
Country: USA
Vessel Name: Hobo
Vessel Model: Krogen 42-120
Join Date: Nov 2008
Posts: 5,749
RE: Propeller shaft prep for prop

The last time we had a prop at a*shop in*Seattle, the prop guy said it was OK to use Never-seize but he said to use a real light application.* When we hauled-out 2 plus years later the prop nuts were as tight as when I installed them.

Larry/Lena
Hobo KK42
Zihuatanejo, MX
__________________

Larry M is online now   Reply With Quote
Old 12-24-2010, 01:50 PM   #3
Doc
Guru
 
Doc's Avatar
 
Join Date: Oct 2007
Posts: 508
RE: Propeller shaft prep for prop

One yard used some kind of cutting oil on my previous boat, a 45' Californian MY with 485 hp DD's. The guy sat on a box turning the prop on the shaft for about 5 minutes before he installed the nuts.
Doc is offline   Reply With Quote
Old 12-24-2010, 04:20 PM   #4
Senior Member
 
capt jerry's Avatar
 
Join Date: Oct 2007
Posts: 321
RE: Propeller shaft prep for prop

The way i do it is to use valve grinding compound and put it on the shaft and slide the prop on and turn the prop for a while* without the key to get rid of any high spots,then push hard on the prop to make sure that is all the way up without the key,and then mark where it is on the shaft, take the prop off and put it on with the key in it , and make sure it goes all the way up to the mark,if it dont then you have to file the key i little till it goes all the way.if you dont it might become key bound, and you could get a vibration,because the prop is riding on the key instead of the taper
capt jerry is offline   Reply With Quote
Old 12-24-2010, 05:12 PM   #5
Guru
 
City: North Charleston, SC
Country: USA
Join Date: Sep 2010
Posts: 4,390
RE: Propeller shaft prep for prop

Quote:
capt jerry wrote:

The way i do it is to use valve grinding compound and put it on the shaft and slide the prop on and turn the prop for a while* without the key to get rid of any high spots,then push hard on the prop to make sure that is all the way up without the key,and then mark where it is on the shaft, take the prop off and put it on with the key in it , and make sure it goes all the way up to the mark,if it dont then you have to file the key i little till it goes all the way.if you dont it might become key bound, and you could get a vibration,because the prop is riding on the key instead of the taper
You clean the valve grinding compound off before the final installation, right?

*
rwidman is offline   Reply With Quote
Old 12-24-2010, 07:42 PM   #6
Doc
Guru
 
Doc's Avatar
 
Join Date: Oct 2007
Posts: 508
RE: Propeller shaft prep for prop

Valve grinding compound. That's what I meant.
Doc is offline   Reply With Quote
Old 12-24-2010, 09:05 PM   #7
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,723
RE: Propeller shaft prep for prop

capt jerry,That's the way I've done it except once. I think I was "key bound" a bit. Must have had a lapse or was in a hurry. Some vibration resulted.*I'd always put them on dry but the local mechanic said use Never-Seize. So I tried it but it wasn't long before I needed to pull it off and it did come off easily but that may have been related to the key bound situation. The only way I can imagine the Never-Seize being a problem is if the shaft and prop were to move back and forth causing wear but Larry's experience suggests that dosn't happen. If so I think the boat mechanic here was right.
Use Never-Seize.
Attached Thumbnails
Click image for larger version

Name:	sth71268.jpg
Views:	75
Size:	132.6 KB
ID:	3906  
Nomad Willy is offline   Reply With Quote
Old 12-25-2010, 06:53 AM   #8
Senior Member
 
capt jerry's Avatar
 
Join Date: Oct 2007
Posts: 321
RE: Propeller shaft prep for prop

  1. yes you clean the compound off the shaft before you put the prop on,i worked for Staten Island Boat sales on and off as a dilevery captain fo 30 yrs,and thatwas the way we did it in the yard ,,i have done over 200 deliverys for them back* and forth to florida* and west coast* of florida.and had quite a lot of prop problems on some of those trips,running a ground once in a while.** but they say you havent been* around till you* have been aground** LOL
capt jerry is offline   Reply With Quote
Old 12-25-2010, 07:35 AM   #9
Scraping Paint
 
City: Fort Lauderdale
Vessel Model: CHB 48 Zodiac YL 4.2
Join Date: Oct 2007
Posts: 3,804
RE: Propeller shaft prep for prop

After cleaning off the lapping compound, coat the taper with machinist's bluing then trial fit the prop. The bluing will show the area of contact. Typically, 85 percent contact or better is considered a good fit.
RickB is offline   Reply With Quote
Old 12-25-2010, 11:07 AM   #10
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 16,534
RE: Propeller shaft prep for prop

Great now that it fits , will we resume the big nut inside vs the small nut inside war?

MY way,
Big nut , big wrench to seat the prop, then take OFF the big nut , install the thin nut reasonably tight , then the big nut really tight up against the small nut.

Other religions?
FF is offline   Reply With Quote
Old 12-25-2010, 11:27 AM   #11
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,723
RE: Propeller shaft prep for prop

Is the smaller nut not a lock nut of sorts? The bottom line here is to hold the prop on so why on earth put the small nut on first? I've heard it's the propper way to do it but it seems so bass akwards I still don't put the small one on first because I can never remember the why. OK*** ...I'll bite FF***** .....why?
Nomad Willy is offline   Reply With Quote
Old 12-25-2010, 11:41 AM   #12
TF Site Team
 
Larry M's Avatar
 
City: JAX, FL
Country: USA
Vessel Name: Hobo
Vessel Model: Krogen 42-120
Join Date: Nov 2008
Posts: 5,749
RE: Propeller shaft prep for prop

Quote:
FF wrote:

Great now that it fits , will we resume the big nut inside vs the small nut inside war?

MY way,
Big nut , big wrench to seat the prop, then take OFF the big nut , install the thin nut reasonably tight , then the big nut really tight up against the small nut.

Other religions?
What no cotter pin?*

*
Larry M is online now   Reply With Quote
Old 12-25-2010, 03:40 PM   #13
Guru
 
Tidahapah's Avatar
 
City: Mooloolaba
Country: Australia
Vessel Name: Tidahapah
Vessel Model: Bert Ellis Timber motor cruiser
Join Date: Oct 2007
Posts: 1,779
Propeller shaft prep for prop

Depends on size of prop & shaft but for mine there is no lock nut, big boss nut with a 1/4" brass rod thru nut and shaft bent over each end.
Here we go a little photo for description.
Benn

-- Edited by Tidahapah on Saturday 25th of December 2010 09:18:11 PM
Attached Thumbnails
Click image for larger version

Name:	p1150067.jpg
Views:	82
Size:	147.4 KB
ID:	3911  
Tidahapah is offline   Reply With Quote
Old 12-25-2010, 06:51 PM   #14
Senior Member
 
capt jerry's Avatar
 
Join Date: Oct 2007
Posts: 321
RE: Propeller shaft prep for prop

For yrs and yrs all the older Bertrams from the factory* had the small nut on first
capt jerry is offline   Reply With Quote
Old 12-25-2010, 10:59 PM   #15
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,723
RE: Propeller shaft prep for prop

Why
Nomad Willy is offline   Reply With Quote
Old 12-25-2010, 11:31 PM   #16
Guru
 
Tidahapah's Avatar
 
City: Mooloolaba
Country: Australia
Vessel Name: Tidahapah
Vessel Model: Bert Ellis Timber motor cruiser
Join Date: Oct 2007
Posts: 1,779
RE: Propeller shaft prep for prop

Eric,
Yes Why.
A nut requires its dia in depth for any holding power.
A 5/8 nut must be 5/8" deep
A lock nut is usually a 1/2 nut tightened up on top of the full nut.
Go figure!!!
Benn
Tidahapah is offline   Reply With Quote
Old 12-26-2010, 06:58 AM   #17
Scraping Paint
 
City: Fort Lauderdale
Vessel Model: CHB 48 Zodiac YL 4.2
Join Date: Oct 2007
Posts: 3,804
RE: Propeller shaft prep for prop

The thin nut is a jam nut. It purpose in life is to prevent the larger load bearing nut from backing off. It goes on first.

The way it works with props is the large nut is used to push the prop tightly on the taper. It is then removed and the thin jam nut is torqued to about half of its rated torque. This is just to ensure that the nut is hard against the prop hub and its threads are loaded. The jam nut is held with a wrench and the large nut is then tightened against it.

What happens is the threads on the jam nut are at first in contact with the loaded or working side of the threads, picture the nut pulling itself down the shaft by gripping one side of the threads. A nut works because torque on the threads creates a tensile load on the shaft or bolt, it stretches it. The parts are held together because the shaft or bolt wants to spring back and whatever is between the nut and the shaft gets squeezed and held by that tension. The torque figure you use or how much umph you twist the nut or bolt depends on how much load the fastener can take before it breaks in tension, or breaks across the threads because of torsional failure or thread stripping. The figure for tension or elongation is calculated by the loads imposed on the shaft or bolt by the machinery it is holding together.

Head bolts must withstand the forces of compression and combustion that want to separate the head from the block. The bolts are tightened so that the force holding the head on is several times higher than those trying to lift it off. If the tension is not high enough, the forces will stretch the bolt each time the cylinder fires and then when that pressure is relieved, the bolt is actually loose for a moment and vibration will loosen the bolt. The best way to prevent firing pressure from stretching the bolt is to pre-stretch it more than the engine can.

Anyway, back to the jam nut. When the jam nut is in place it is applying a force toward the propeller. That force comes from the contact of its "forward" thread surface on the "aft" thread surface (we can use those terms because the shaft is horizontal and we are moving the prop forward) of the shaft. Most of us know that there just aren't enough threads on the jam nut to hold the prop on without strippiing and this is where the controversy comes from. The job of the jam nut is not to hold the propeller on, it is to prevent the prop nut from loosening.

The prop is held securely because when the prop nut is torqued fully it pushes the thread contact area of the jam nut off the "aft" threads of the shaft and unloads the jam nut threads completely. Torgue applied to the prop nut stretches the shaft by pushing against the jam nut which in turn pushes against the prop hub until the jam nut threads contact the "forward" thread face of the shaft. This jams the two nuts together preventing any movement between them.

It's not religion, it's mechanics.
RickB is offline   Reply With Quote
Old 12-26-2010, 10:07 AM   #18
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,723
Propeller shaft prep for prop

Rick,
You're the head gear head from now on. That's the best explanation I've ever heard. So the jam nut just sit's there jamming the two nuts and keeping the load on the big nut that is capable of holding the prop on YES! If the jam nut is installed last the big nut transfers part of it's load to the jam nut but if the big nut goes on last the jam nut transfers it's load to the big nut so the big nut holds the prop on AND carries the jam nut load as well.
Did I get it?
The part that most frustrates me most about propeller installation is the cotter pin, the hole in the shaft and the hole in the big nut. It seems most of the time the when the nut is torqued the right amount the holes are as far out of alignment as possible! Then I over tighten the nut, put the cotter pin in the holes and back off the nut until the holes prevent movement of the cotter pin. I've often thought of drilling more holes in the nut but never have. Is the properly installed jam nut without cotter pins as secure as with the cotter pins? I think there are shim washers to solve the hole alignment problem.
Never seen'em though. Is this the answer or what???


-- Edited by nomadwilly on Sunday 26th of December 2010 11:07:45 AM
Nomad Willy is offline   Reply With Quote
Old 12-26-2010, 12:54 PM   #19
Senior Member
 
capt jerry's Avatar
 
Join Date: Oct 2007
Posts: 321
RE: Propeller shaft prep for prop

i had to use shim washers on a boat that i had,because i put on* prop of differnt make, as the hub was shorter. igot it from a prop shop that had diff. sizes
capt jerry is offline   Reply With Quote
Old 12-26-2010, 01:54 PM   #20
Doc
Guru
 
Doc's Avatar
 
Join Date: Oct 2007
Posts: 508
RE: Propeller shaft prep for prop

capt jerry

Please see the OFDE post on capitalization.
__________________

Doc is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
prop size and shaft, rudder olesouth Power Systems 7 02-22-2012 11:08 PM
Greasing propeller shaft markpierce Power Systems 3 11-18-2011 03:35 PM
A singing propeller markpierce Power Systems 20 09-08-2011 12:26 AM
Propeller Antifouling Jib73 General Discussion 13 06-04-2009 05:34 AM
Prop Shaft Packing joesmainship Power Systems 5 10-11-2007 10:17 AM




All times are GMT -5. The time now is 02:51 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012