Prop re-installation tips.

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Whiskymac

After spending four days over the last three weeks on my cutlass bearing project, interspersed with redesign and rebuild of my boat yard friend's homemade bearing "pusher", we finally completed the project bar the final re-installation of the prop.
I have made a couple of searches but haven't managed to answer my questions regarding torque/tightening of the castellated nut and whether any type of grease/ lube can be used which would make future removals (of the prop) easier.

Thanks,

Jeremy.
Jeremy Lewis. 1988 C-34 #711. Standard rig, shoal draft
Yanmar  3GM30

KWKloeber

Look at mainesail's website - he shows how to lap a prop.
YBYC but you should use the lapping process.  It IS NOT the keyway you depend on, it's the precise fit between shaft ad prop hub.

kk
Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

Whiskymac

Thanks KK, I did read Maine Sail's article before I started but I ran into the following issues:

1. I had trouble sourcing Prussian Blue. I went to 4 different auto stores and no one had heard of it. I'm sure this isn't terminal as I'm sure I could find it online, I just wasn't certain whether this was for re-install or only for fitting a new prop.

2. He refers to tightening to the "proper" torque but does not specify an actual torque. I'm assuming this is because it is different for different shaft/nut sizes?

3. His photos show the use of two nuts, one thinner and one thicker and castellated, my boat has only the thicker one. Are our boats set up differently or could it be that mine is not configured correctly?

Thanks,

Jeremy.
Jeremy Lewis. 1988 C-34 #711. Standard rig, shoal draft
Yanmar  3GM30

KWKloeber

I'm surprised NAPA didn't stock it. Lapping should be done both on new installs and refitting.  Who says it was lapped properly when it was first installed, anyway?

The most secure is to use a lock (jam) nut but yes, it's probably the exception especially on Catalina's.  I have an article about locking on the prop - I will post it as soon as I get back to my pc on wed.

ken
Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

lazybone

Quote from: KWKloeber on May 01, 2017, 12:09:39 PM
Look at mainesail's website - he shows how to lap a prop.
YBYC but you should use the lapping process.  It IS NOT the keyway you depend on, it's the precise fit between shaft ad prop hub.

kk

On my 34 the opposite end of the shaft at the trans coupling relies almost entirely on the keyway to deal with the radial loads.  The set screws there are for axial loads.  The shaft twist some to dampen the shock load but they pretty much mirror the forces at the prop.

Bigger shafts and props have larger stresses But... anyway,  proper practice is to lap the prop.   8) 8)
Ciao tutti


S/V LAZYBONES  #677

Bill Shreeves

Whiskeymac.  Found Permatex 80038 Prussian Blue Fitting Compound from amazon dot com for less than $6.  I'll be ordering it today since my new prop should be shipping to me soon.
The only thing that always works on an old boat is the owner...

Bill Shreeves
s/v "Begnnings" 1987 Shoal Draft #333
M25XPB, Worton Creek, MD

lazybone

You can use any Sharpie marker as a wear indicator.
Ciao tutti


S/V LAZYBONES  #677

Bill Shreeves

Whiskeymac - I re-read mainsails post and I'm wondering if he might be using the term 'torque' as a description to tighten it until the "thin" sharpie marker line disappears rather than to a specific ft lbs.
The only thing that always works on an old boat is the owner...

Bill Shreeves
s/v "Begnnings" 1987 Shoal Draft #333
M25XPB, Worton Creek, MD

KWKloeber

Here's the article I promised about using a locking nut.....

http://www.boltscience.com/pages/twonuts.htm

Prop nut torque depends of course on the shaft/nut size, but for our 1-inch shafts somewhere around 40-50 ft-lbs is good.  I believe I used 45 ft-lbs 20 years ago, and it's still on there :shock::shock: (I think)

kk


Quote from: KWKloeber on May 01, 2017, 11:48:41 PM
I'm surprised NAPA didn't stock it. Lapping should be done both on new installs and refitting.  Who says it was lapped properly when it was first installed, anyway?

The most secure is to use a lock (jam) nut but yes, it's probably the exception especially on Catalina's.  I have an article about locking on the prop - I will post it as soon as I get back to my pc on wed.

ken
Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

Bill Shreeves

KK - Great info but, thats torque to put on the second nut to lock the two nuts, or the one furthest aft, not the torque on the first nut "pressing" the prop on the tapered shaft which is what I thought the question was.  The more I think about it, the prop manufacturer has to have a spec for the torque to hold the prop on the shaft.  That crap isn't left to "tighten her good and firm my man and a wee bit more".  I hope to be getting my new prop shipped to me next week and if there's no info with it regarding the torque, I'll call the mfg and share what I find out.
The only thing that always works on an old boat is the owner...

Bill Shreeves
s/v "Begnnings" 1987 Shoal Draft #333
M25XPB, Worton Creek, MD

KWKloeber

Why not simply call the factory!?!? 
CTY installs props every day of the week (or used to every day).

kk
Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

Whiskymac

Good idea KK. I have a calll in to CTY and will report back when I get a response.
Jeremy Lewis. 1988 C-34 #711. Standard rig, shoal draft
Yanmar  3GM30

Whiskymac

Ok, here's the scoop.

I followed KKs advice and called the factory.

I spoke with Warren who told me no one had ever asked about the torque to be applied to the prop nut and that most experienced yards just knew roughly how much force to apply (which I found a little odd considering the tendency of many owners to want to do as much maintenance work themselves as they can). He also felt that I should definitely have a "two nut" system rather than the single castle nut I found on my boat. He suggested I follow up with General Propeller in Florida and/or with Michigan Wheel Propellers.

I called General Propeller first and cleared things up quickly. Either the 2 nut system or the single castle nut are OK and he said ( as Bill suggested) that there is no torque value to apply but just tighten until "tight" and adjust enough to be able to insert the pin. I forgot to ask the process for the 2 nut system.

I also managed to source the Prusssian Blue from another Napa store so I think I'm now set up to lap fit the prop back to the shaft this weekend.

Thanks to all for the advice.
Jeremy Lewis. 1988 C-34 #711. Standard rig, shoal draft
Yanmar  3GM30

KWKloeber

Jeremy,

unbelievable that no one "in the know", has a clue!   :shock: :shock:

The MAXIMUM torque value for a 3/4" brass bolt/nut is around 100 ft-lbs (depending on whose chart you use.)  I figure the controlling factor is the brass nut, not the stainless shaft.  So I used about half the MAX value -- 50-ish -- as a working value.  Someone poo-pooed that, but that's my story and i'm stickin'toit.   :D

Ken
Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

lazybone

Its a 1" shaft turned by a small toy like engine. Maybe we're over thinking this.  I mean really, the whole "a keyway is not enough", "you have to lap the prop", "what's the exact torque value on each nut".  Please stop.
Ciao tutti


S/V LAZYBONES  #677