What do you called this nut - crown or castle?

[ericoh88]

Hi,

My prop caught a stray fishing net during my last trip out. The crown nut was seized against the rudder by the net which sheared the small cotter pin and sheared the thread in the crown nut.

I have attached a picture of the nut. I don't have a spare so I am getting the machine shop to make one in bronze. Before I go ahead, I have a few questions.

1. What do you call this nut? where can I buy one of this nut? How much does one cost?

2. I saw on https://www.generalpropeller.com/inb...Shaft-Nut-Kits that they use brass. I thought I have to use bronze material only. Can one use brass for salt water use?

3. What is your set up? A large single bronze crown nut with cotter pin or you would prefer two nut with a cotter pin?

My shaft is 1 3/8" diameter . The thread gauge is British No 9. Outer diamter for the thread is 22.5mm and inner diameter for the thread is 19.5mm.
The shaft thread won't fit the standard 1", 3/4" or 7/8" nut. So a sample shaft thread and matching nut were being machined.

Thank you in advance.

Eric

[Alan Mighty]

Originally Posted by ericoh88

2. I saw on https://www.generalpropeller.com/inb...Shaft-Nut-Kits that they use brass. I thought I have to use bronze material only. Can one use brass for salt water use?

I've not seen your genre of nut before. So I'll just answer your Q. 2, Eric.

Yes, propeller nuts on stainless steel prop shafts are usually (often? mostly?) brass.

The brass is usually a manganese bronze, but that's a brass.

Reasons for the brass prop nuts:

1. so the prop nuts are not cathodes to your bronze propeller (i.e. you'd rather sacrifice your prop nuts to protect your prop than vice versa) especially if your "bronze" propeller is also really a brass (as many are).

2. so the prop nuts do not gall or cold-weld themselves to the threads of your stainless steel prop shaft. If you used stainless steel nuts on a ss shaft, the tightening torque could lead to galling (cold welding). Brass nuts on stainless steel threads are slippery and smooth and so do not cold weld, even when tightened. And brass is even more slippery on ss than bronze nuts.

A shaft anode protects the nuts, the prop, and the shaft.

[Orion Jim]

It's a brass nut, part of a prop nut anode kit.
Camp Company :: Propeller Anodes :: Propeller Nuts :: Brass Nut Kit

[RobTryon]

I've heard it called a Sperry nut, it holds a Zinc for boats that have the shaft in an aperture.

[deblen]

Further info How to attach Prop Nut Zinc? - SailNet Community

[ericoh88]

I have had many dives to trying figure out the thread and and diameter - all underwater. The information given here awesome.

Alan Mighty - the brass that I am familiar is the brass that is used in the household water piping taps. Thanks.

Orion Jim - This is spot on. Mine should be DN 7/8" 9 . I bought a nut 7/8" and the standard thread just won't fit. Now I know these things are available and not custom made. Thanks.

RobTryon - I heard someone at the yard mention crown nut. Sperry nut. Brass nut. Another new word for my books. Thanks.

deblen - good info - thanks.

This is where the problems starts. This is the first time I attached a zinc anode on the "Brass nut/Sperry nut" making the slot to the rudder very tight. This is how the stray fishing net got wrap around and the whole zinc anode got grabbed by the rudder blade resulting in a fixed "Brass nut/Sperry nut" and a turning shaft.

Something has to give way. The cotter pin and the softer thread in the nut.

Isn't CF such a cool place to learn. Thank you again for your replies.

Eric

[deblen]

If your shaft is 1 3/8" diameter,the nut thread should be 1" x 8 thread per inch. / Len

https://propshopinc.com/Nut-Kit-Set-...llers-p30.html

[ericoh88]

Just an update. I call Camp at 727.397.6076 and spoke to Mark Camp who strongly recommend that I use the 2 nuts to lock the propeller instead of my old set up of a brass / sperry nut.

Eric

[ericoh88]

Originally Posted by deblen

If your shaft is 1 3/8" diameter,the nut thread should be 1" x 8 thread per inch. / Len

https://propshopinc.com/Nut-Kit-Set-...llers-p30.html

deblen - appreciate your comment. The specs for this boat from manual is 1 1/4" but the shaft after the gear box is 1 3/8" or 35mm . The shaft was tapered for the propeller . I measured the outer diameter for the thread is 22.5mm which is 7/8" with british thread no 9 using a whitworth thread gauge for imperial and metric.

The machine shop managed to machine a shaft 22mm with no 9 thread and a sample nut which fits perfectly on the prop shaft. So I am happy. Thank you again for your comment.

Eric

[Sailorbob8599]

Originally Posted by ericoh88

Hi,

My prop caught a stray fishing net during my last trip out. The crown nut was seized against the rudder by the net which sheared the small cotter pin and sheared the thread in the crown nut.

I have attached a picture of the nut. I don't have a spare so I am getting the machine shop to make one in bronze. Before I go ahead, I have a few questions.

1. What do you call this nut? where can I buy one of this nut? How much does one cost?

2. I saw on https://www.generalpropeller.com/inb...Shaft-Nut-Kits that they use brass. I thought I have to use bronze material only. Can one use brass for salt water use?

3. What is your set up? A large single bronze crown nut with cotter pin or you would prefer two nut with a cotter pin?

My shaft is 1 3/8" diameter . The thread gauge is British No 9. Outer diamter for the thread is 22.5mm and inner diameter for the thread is 19.5mm.
The shaft thread won't fit the standard 1", 3/4" or 7/8" nut. So a sample shaft thread and matching nut were being machined.

Thank you in advance.

Eric

Are you sure that is a single one piece nut? It looks more like a standard Flanged Prop Nut with a locking Dome Nut to me. And if you cannot find such a fastener why not use a standard flanged nut and a dome lock nut?
My prop is secured with only the standard flanged nut with a cotter pin through the threaded tail section of the shaft.

[Orion Jim]

Originally Posted by Sailorbob8599

Are you sure that is a single one piece nut? It looks more like a standard Flanged Prop Nut with a locking Dome Nut to me. And if you cannot find such a fastener why not use a standard flanged nut and a dome lock nut?
My prop is secured with only the standard flanged nut with a cotter pin through the threaded tail section of the shaft.

See #3 above for the answer to your query.

[fstbttms]

FYI- a Perry Nut (not "Sperry") is similar to the standard cap anode and cone nut arrangement pictured above except that the anode is cast directly on to the nut. They are not individual components and when they are replaced, both the nut and anode must be replaced.