Loose Wheel

Whoops

Whoops

New Member
Oct 10, 2006
43
Algonac, Michigan
Boat Info
400 Sundancer 1997
Engines
3116 Caterpillars
For the last 2 years at haul out the starboard prop nuts loosened back to the cotter pin. Can't believe that I can get the nuts much tighter, is it possible that I need a new key? Has anyone else run into this problem. Starboard side only, no problem with the port side.
 
Whoops said:
For the last 2 years at haul out the starboard prop nuts loosened back to the cotter pin. Can't believe that I can get the nuts much tighter, is it possible that I need a new key? Has anyone else run into this problem. Starboard side only, no problem with the port side.
Click to expand...

What order are you putting on the nuts. Skinny fat or fat skinny?
 
Whoops said:
For the last 2 years at haul out the starboard prop nuts loosened back to the cotter pin. Can't believe that I can get the nuts much tighter, is it possible that I need a new key? Has anyone else run into this problem. Starboard side only, no problem with the port side.
Click to expand...

I have not run into this problem, and I have limited experience with inboard prop shafts,(very limited) but my props are currently off my boat and I will be putting them back on in the spring, if it ever gets here, so I am interested in this thread.
You may need a new key, or your keyways may be damaged, so a close inspection is warranted, but if they are damaged, I would think it would be because the prop nuts loosened and allowed the prop to "work" on the shaft, possibly causing rounding of the key or keyways. As far as why they loosened in the first place, assuming the nuts and shaft threads are in good shape, a couple of things come to mind, first, I have always been told grease on outdrive shafts, no grease on inboard shafts. The inboard is a taper fit and you don't want a film of grease between the hub and shaft that will eventually disappear and possibly cause the prop to move ever so slightly forward, causing the connection to loosen.
Secondly, and what I would be most suspect of, is the nuts not being jamed properly, and I am hoping someone who has more experience jumps in. As David mentioned, nut sequence can make a difference. Because I have to install my props, I was looking in the manual a while back and it says to put the "large" nut on first, and torque to spec, then put the jam nut on and tighten. This is the opposite of what we do here in our shop, (not marine business), the half nuts go on first, torque down, and then jam the connection with the full nut. which means to use 2 wrenches and jam the nuts together, not just tighten down the first nut and then tighten down the second nut on top of it. There are specific things that happen to the thread on the shaft when this is done correctly that causes the two nuts not to loosen, which I won't get into because this post is already to long.
So how about it, more experienced prop installers, is my sea ray manual wrong on the prop nut sequence?
Bill, what was the sequence on yours?
Am I looking in the right direction here, or are there other possibilities that could be at play?
Thanks in advance.
 
No grease is correct. It's a machined fit. I don't know what nut is used to snug the prop and torque to spec, but the final setup on mine and verified by local SR mech is prop, skinny, fat. I don't recall the engineering / reasoning why but it is just the opposite of what I would have thought.
 
dpmulvey said:
No grease is correct. It's a machined fit. I don't know what nut is used to snug the prop and torque to spec, but the final setup on mine and verified by local SR mech is prop, skinny, fat. I don't recall the engineering / reasoning why but it is just the opposite of what I would have thought.
Click to expand...

What your SR tech says is the way I was always taught.
My owners manual for my boat clearly says that the "large" nut goes next to the prop. I can't remember what the two nuts look like, unless maybe the thin one is "larger" diameter :huh: I will have to drive by the boat yard and look.
The reason it works has to do with the thin nut having less bearing area on the thread lands than the thick one, and when tightened together, the strain on the threads (in opposite directions), puts the bolt (shaft) in tention between the two nuts, the threads distort differently under the thin nut vs the thick one because of the difference in "surface area" of the thread contact, which is what locks them together.
(reading back over that, it seems as clear as mud..sorry)

So back to the OP..maybe the nuts were reversed??
If the thin nut is on the outside, it can't be tightened enough to overcome the thrust of the load (prop), and put enough tention between the two nuts to lock them, without stripping the threads out.
 
my3sons said:
My owners manual for my boat clearly says that the "large" nut goes next to the prop. I can't remember what the two nuts look like, unless maybe the thin one is "larger" diameter :huh: I will have to drive by the boat yard and look.
quote]

ThruHull.jpg


That answers that question, and saved me a trip...Thanks Vince. :thumbsup:

Owners manual is wrong :smt009
__________________
Click to expand...
 
Mark, David, Second Chance,

Thank you all for your feed back. I spoke to a tech at Henry Smith & Co. and was I advised to first perform the check that Second Chance advised. Most likely the key is stopping the prop from seating in the proper position. They also advised that the large nut go on first against the prop and the thin nut second as the jam nut. We will see this weekend and I will report back to you all. Many thank's !
 
Whoops said:
They also advised that the large nut go on first against the prop and the thin nut second as the jam nut. !
Click to expand...

:smt101 This seems to be a topic of mixed opinion.

Did they install the nuts last time, in that order, and then they loosened?
Keep us posted
Thanks
 
Your props need to be lapped. Even if they were okay before, having worked loose, they're not going to fit the shaft properly. Did a quick google and found this as #1. Seems okay except he uses a block of wood to keep the prop from turning. Not a good idea if you have your props scanned and trued.

Best regards,
Frank

http://www.pbase.com/mainecruising/fitting_a_prop
 
The best way i have found to keeping
big prop nut tight is to tork down then warm prop with heat gun or propane plumbers torch to 70 or 80 when it is 50 out side and then retork at least 1-4 turn. Do the same heat when removing props with puller and it will pop off with little effort.
 
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The PDF and Pix is the way mine is set up. No problems in 3 years. Quite the opposite. The props seated so well you would think the prop and shaft were one piece.
 
I couldn't get the linky that techmitch provided to work so I went to Michigan Wheel's website and found a .pdf that shows their installation procedure. http://www.miwheel.com/uploads/resources/Inboard_Installation_Process.pdf

It clearly shows the skinny nut going on first, then the fat nut, then the cotter pin. I checked photos of my boat when it was reassembled after the transport and that is the way the boat yard did it. I'm glad to see the yard did it the recommended way.

P71500141-1.jpg



GFC
 
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