Prop nut -- unusual?

AZ2Loop said:

Among a thousand other projects, while our boat is out of the water I was planning on pulling the props off to do a general inspection/cleaning/etc. to get familiar with how they come off and go on. Our previous boats were stern drives, so this is new to me. In passing, a guy at the yard commented on the unusual prop nuts on our trawler. I don't know if these are unusual or not, but his comment made me wonder. Before I start pulling these apart, is this an unusual setup? Am I tearing into/pulling apart anything that might be difficult to get back together? Here is a picture of one of our props. They are 24" props, and I do not yet know the pitch. Boat is a 1990 49' Albin with twin 250 Cummins 6BTA's, 2" shafts, Velvet Drive transmissions. In our short sea time so far there are no known issues or vibrations with the props. I just like to pull things apart, clean up, and get familiar with how they go together for peace of mind. It seems like a good time to get familiar with this "business end" of our new (to us) boat. I would think this is a wise move to inspect now and gain an understanding of how this goes together vs learning under less than ideal circumstances while in the water. Am I just opening a can of worms? Seems like it should be simple.... but I am open to advice. Thanks for any thoughts.

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kchace said:

It is NOT a zinc or a cover, it is a solid brass nut. I have the same prop nut on my boat and have removed it a few times. There is nothing weird or complicated about it. Remove the center bolt which acts as a lock and unscrew the giant nut. The center lock bolt should have a locking "washer" on it, but since they're SS and have to be bent, they only last maybe 4-6 times. Fortunately, its easy to make a new one with a hacksaw and a piece of stainless.


See attached pictures.



Ken

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diver dave said:

I've never seen one. I suppose this one avoids the entire heavy nut/jam nut argument!

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kchace said:

As has been stated, you WILL need a prop puller. Unlike stern drives, props on shafts like this are installed on tapers which make the props fit the shafts very tightly. So the prop will not slide off when you take off the nut - if it does, you have a serious problem. You can borrow, buy or make a prop puller.

Below is a picture of the prop puller I made. They are easy to make and work great.


edit - I would not pull the props off for no reason. With the right tools they are easy enough to remove, but re-installing them requires proper cleaning of the tapers, keys and keyways involved.


I WOULD make and install proper lock washers onto the center lock nuts.


Ken

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Todd2 said:

At first I thought it was a zinc like my setup. Mine has a brass prop nut that looks sort of like a castle nut, except the fingers of the "castle" form a bucket that extends over the end of the shaft. The very back end of the nut (not the shaft) has a threaded hole for a bolt to hold the zinc on (assembled, it looks like the pics above). A cotter pin through the shaft locks the castle portion of the nut from loosening on the shaft (before installing the zinc).


I don't really like the design that much, as there is very little room to fit the cotter pin under the zinc. Also, as the zinc corrodes the bolt would loosen, so an ample amount of thread locker is required. At least there's no jam nut.


Is this a common set up?


Todd

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Comodave said:

I made one as shown in the photo. I have no idea how long the props had been in place. I tightened the bolts a much as I could and my starboard prop would not budge. I let it sit for about 15 minutes and tried it again. It let loose with a bang that sounded like a gunshot. The port prop came off quietly and relatively easy compared to the starboard.

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AZ2Loop said:

Thank you all for your responses. This is such a great forum. I appreciate all of the advice, photos, information, etc. I'll let you know if I get into it end up tearing anything up! KChace, I really appreciate the tip on the lock washer. I'll see if I can fabricate something like that. So much to do!

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kchace said:

Well, the plates are 1/2" steel and there is also a filler for the slot in the rear plate. The screws are 1/2" grade 8 fine thread - the nuts and washers are also grade 8. If tightened quite tight, the clamping force would be about 15000 lbs each. With this setup, all I need is a standard hand wrench to pop off the prop.

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firstbase said:

Have never done this using a prop puller home made or otherwise so excuse my newb question...when you are tightening the 4 bolts to remove the prop, generally speaking how much do you turn each nut at a time? 1/2 turn, full turn? Just go by feel or tightness? Know it would depend somewhat on the number of threads for the bolts. Imagine that putting too much pressure on one corner alone is not a good thing.

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Comodave said:

Here is a photo of the prop puller I made. It is for a 4 blade prop. Put the plate with the slot forward of the prop and the solid plate on the end of the prop shaft. Insert the 4 bolts and tighten up securely. I just work my way kitty corner torqueing them as tight as I can and then wait a bit and go again. One of my props came off with a bang and the other with a whimper. The puller holds the prop on when they pop off so it doesn’t drop to the ground. My shafts are 2” so the slot is about 2 1/8”.

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Comodave said:

Can you replace the unusual nut with the regular double nuts or do you have to stay the OEM nut? Just wondering if the nut were to get damaged or float to the bottom during an in the water prop change are the OEM nuts available?

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