Poised for the perfect docking manoeuvre... engage astern... and there goes the propeller...

[Martin_J]

I have a castellated nut & split pin - supplied when I fitted a new shaft & prop after fitting a new engine.

The original post is about a Volvo saildrive.

Is your castellated nut on a Volvo saildrive shaft? If so, which model...

 

[Martin_J]

I did hear that a replacement cone is a different design and does away with the need for the plastic washer..

Another quick check online shows that there are now more than one 'new' designs of cone and fixing..

 

[Martin_J]

So has the tab washer kit gone, the old kit also gone and now we're left with just a new kit that includes cone and bolt only?

 

[MagicalArmchair]

So has the tab washer kit gone, the old kit also gone and now we're left with just a new kit that includes cone and bolt only?

And that is what mine was, with the just the one locking bolt with blue locktite on it. The whole point of locktite is that it can be disassembled, especially the blue stuff that is specced, then just like Elon Musks Starship, it chose that moment as we entered the berth for "a rapid unscheduled disassembly". You would think there would be something positive and mechanical (like the tab washer - what a perfect solution) to prevent this kind of situation.

I suppose the solution is to:

• Make certain all threaded surfaces are completely, completely clean. Easy to do with the bolt (you could replace it each time).- harder to clean the thread in screws into perfectly and fully. Any thoughts on how that could be achieved?
• Use lashings of red locktite. You then have the potential to seize the whole lot up, although with a bit of heat, I've never had a problem with the "permanent" stuff.

Any other tips? Any method to retrofit a tab washer?

Diver booked in on Thursday. MDL here have been very helpful, the insurers very pleasant, RHYC most helpful (and found me the diver) and Fox's upriver (who will be doing the lift) very accommodating also.

 

[Martin_J]

I always held the cone firm whilst doing the final tighten of the bolt, on the assumption that the bolt was being used like a second nut might be used to lock a first nut (on a bolt or stud). You always hold the first nut still whilst tightening the second.

I guess some just hold the prop firm whilst tightening the cone and then still hold the prop firm whilst tightening the bolt.

I assumed this wouldn't lock the bolt to the cone (just like it wouldn't lock two nuts together).. or are my thoughts and assumptions way off the mark.

I'd love to hear because I always wondered why there wasn't a castellated nut and associated pin.

Someone earlier did say that it might be tricky drilling through the saildrive propshaft.

Why then when I look back at photos, it's there a hole drilled in what looks to be a near perfect place for securing a castellated nut?



It does look a very short thread to hold the cone on.. and a hole that's not really used!

 

[Tranona]

When my first saildrive boat was on charter the Greek management used a cone they made themselves with a bolt through that hole. Crude but presumably was considered reliable. i replaced it with a standard cone when It took the boat over. While it is known that the locking bolts do come undone, given the tens of thousands of drives in use the number is probably very low. The real answer is fit a flexofold prop which has a lock nut!. My understanding is that the delrin washer is there to insulate the prop and spinner from the shaft. I have not seen the new cone, but maybe it has an insulated face.

 

[MagicalArmchair]

I have purchased a new locking machine screw that comes with red thread sealant. I also purchased from VolSpec some degreaser (to clean the shafts female thread), and some additional Volvo thread sealant, and I have a little pipe cleaner I'll use too clean it out too.

I've read horror stories of boats having lost FOUR props in this way! What about applying thread sealant to the cone thread itself too? It means it would need a blow torch to get it off, but having the locking screw thread locked AND the cone threads thread locked has got to be secure?

 

[penfold]

When my first saildrive boat was on charter the Greek management used a cone they made themselves with a bolt through that hole. Crude but presumably was considered reliable.

A bit clunky but they obviously liked it enough; if I was unlucky enough to have one of these I might try drilling axially through the cone once torqued up and into the prop, tap the hole in the cone then a long dog point grub screw will hold the two together. The whole thing is a bit half baked, if they wanted the efficiency gains of a faired hub(pretty de minimis for a yacht auxiliary, but whatever) a longer than necessary threaded section on the shaft would allow a conventional nut and tab washer then a hollow cone can be screwed over the whole thing(and made of plastic to save cost).

 

[Deleted member 478]

I have purchased a new locking machine screw that comes with red thread sealant. I also purchased from VolSpec some degreaser (to clean the shafts female thread), and some additional Volvo thread sealant, and I have a little pipe cleaner I'll use too clean it out too.

I've read horror stories of boats having lost FOUR props in this way! What about applying thread sealant to the cone thread itself too? It means it would need a blow torch to get it off, but having the locking screw thread locked AND the cone threads thread locked has got to be secure?

Did you have any luck with sending a diver down?

 

[penfold]

I have purchased a new locking machine screw that comes with red thread sealant. I also purchased from VolSpec some degreaser (to clean the shafts female thread), and some additional Volvo thread sealant, and I have a little pipe cleaner I'll use too clean it out too.

What degreaser have they sold you? Carburettor cleaner is pretty aggressive and coming in an aerosol is good for cleaning out threaded holes.

 

[Tranona]

Loctite have their own branded cleaner. I looked at it just a couple of days ago as I hade to put some red on the set screw which locks the Kong anchor swivel. However at £14 a can for a one off I decided to just use mechanical cleaning of the new screw. If I lose my expensive new anchor I know who to blame.

 

[MagicalArmchair]

The diver was excellent, however with a foot of silt on the surface, his air ran down and he failed to recover any of the missing parts. I popped back up to VolSpec to find they had a new cone in stock - and it was not what I was expecting. See the attached.

Speaking to the engineers there they said around three years ago they reintroduced the tab washer affair. The only challenge with that tab washer is all that it does is tether the locking screw to the cone... that both presumably could spin off together. There is still nothing mechanically holding the cone to the shaft. The instructions look a bit more scientific, with a proper nut to get a torque wrench onto and torque measurements.

Do we think if I follow the guidance from VP this propeller will stay firmly attached this time?

 

[Martin_J]

Looks like the top item in the diagram I posted in #42.

I'm still intrigued by the middle item in the same diagram that is possibly an even later incarnation.

 

[Martin_J]

At least you can get a socket onto the cone. It was never easy tightening it through the hole.

 

[Martin_J]

Actually.. It was easy tightening the cone using a round bar through the hole... The harder part was then holding the cone still whilst tightening the central lock bolt (because Erth that in place, the bar would then only go part way through the hole)..