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Old 04-03-2018, 06:07 PM   #21
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The yard cut corners when they installed the wheel, no other reason for the nut to loosen. There is supposed to be two nuts, the thin one goes on first and the fat one last and is pinned.

Don't believe everything that you think.
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Old 04-03-2018, 06:17 PM   #22
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Originally Posted by Roger Long View Post

I wish I could install a nut and jamb nut pair but there isn’t enough clearance on this particular shaft.
When you view this again, see how much of the shaft taper is still visible forward of the prop hub. Maybe a chance for a shop to machine the hub to allow it to sit further forward, thereby making room for a proper double nut job.

If there is no extra taper to work with, then maybe machine off some hub on the aft end. I'm sure a prop shop would have good suggestions.

And, of course, make REAL sure the prop is not sitting on the key. I use prussian blue for the test.

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Old 04-03-2018, 07:24 PM   #23
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If you are going to get a new nut, could you order a slightly thinner one to make room for a jam nut ? In other words, if your one nut now is an inch long, order a 1/8 inch jam nut and a 7/8 inch main nut.
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Old 04-03-2018, 07:58 PM   #24
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I would also suspect the fit of key. Even if the prop & shaft are mated properly a key can be problemental.
I would get some blue and ensure fit w/o the key and mark the hub location.
Confirm seating.

I find it hard to believe that erosion / corrosion would not be obvious???
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Old 04-03-2018, 09:47 PM   #25
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Agree that it is likely the key was not seated properly when the nut was tightened and over time the key moved a bit allowing the prop to seat further.
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Old 04-05-2018, 11:30 PM   #26
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Don't assume the prop has not slid further up the shaft. The load from driving may have pushed it up more if the prop hub was riding the key and/or not well fitted to the shaft.

The fact that you have a castellated nut with a cotter pin in it tells me the nut will not have backed off. Most likely the prop does not properly fit the shaft.

Go to Seaboard Marine and look in TONY'S TIPS and look for his article:
Propeller installation / Big Nut vs. Little Nut

Found under the sub heading: BOATS & REPOWERS

THe article cannot be copied to add here.

Pay attention to his description of how to 'Fit a prop to a shaft' with a marker pen and some valve grinding compound, often known as Clover compound.

I had to do that 10-12 years ago. I found my prop was riding the key. After dealing with that and then using the CLover the prop slip another 3/8" further up the shaft. THe cause of the key riding in my case was an improperly cut keyway in the prop hub. It actually had a bit of rocker in it, ie. the keyway bottom was not flat or straight.

Check it out as eventually it could cause some damage.
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Old 04-06-2018, 12:54 AM   #27
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The original post refers specifically to Manganese Bronze which is a specific alloy. It is to me a low zinc brass at about 22% zinc. It is somewhat subject to dezincification. I think you would be better off using a lower zinc alloy.

I consider Maganese Bronze to be brass but Red Brass is really Bronze. Red Brass only has about 5% zinc and is very resistant to dezincification.

Manganese Bronze is used to make propellers but I think its a trade off. They use it despite its high zinc content because it machines very well. Its certainly much better than common brass which has a zinc content of 35% or so.

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