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Old 07-26-2017, 02:40 AM   #21
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Originally Posted by Aquabelle View Post
Brian: 6 bearings is 3 per side. One for the big skeg against the prop; one for the intermediate bearing; and the 3rd.....for the stuffing box?? Maritime archaeology begins tomorrow...


I don't know if the shaft was replaced with the engines. I do know the skeg and intermediate bearing holders have plenty of room to take different thickness cutlass bearings. The new ones (naval brass shells) for the two skegs have to be shimmed down a little to fit, but these things come in different outer wall thicknesses (while remaining constant for shaft of) for just that purpose apparently.
Yes, I believe my stuffing box has the same bearing as the skeg and intermediate strut. And so I doubt there would be rubber in there as well, but I really don't know.
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Old 07-27-2017, 05:56 AM   #22
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Two Steps Fwd, One Aft: I'll cover off progress in a few separate posts. First, the shaft...

Per earlier posts, the shaft was found to be pitted/corroded over the section within & fwd of the stuffing box. I found a now-rare (at least in Sydney) spray welding outfit and took the 3.9m shaft to them and retrieved it 48 hours later. I am really impressed with the work they did, the care shown and the moderate price charged...and the yard engineer was impressed too. I'm happy to recommend Flame Coatings of Ingleburn: Thermal Spraying, Spray Coating, Welding, Arc Spraying | Flame Coatings, Sydney

A pre-treatment photo appears below, along with wide and detail views of the repaired shaft....which is now back at the slipway and ready to be re-installed when SB is ready to accept it.
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Old 07-27-2017, 06:17 AM   #23
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Paul:

Glad the thermal spraying went well. They look to be well set-up and have a lot of expertise. I had some potential crevice corrosion at the SB, which was why I replaced the shafts. Maybe I could have repaired the shafts instead!!

But, as the thread below discusses, shaft failures are very likely more often caused by poor taper fit and particularly keyways. I found the thread very informative.

Shaft broke off at the cutlass bearing
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Old 07-27-2017, 06:27 AM   #24
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Now, the mysterious stuffing box….or not so mysterious, as it turned out to be as I’d guessed in post #18 above. No shipwright or engineer at the yard had ever seen one like this and the DuraMax pdf I attached at post #18 was all they had to go by. An experienced shipwright took it partially apart and discovered two “puller/pusher” tapped holes. Thin flat stainless plates were inserted between the bronze backing plate and the hull (not easy) and threaded rods were then screwed in, which with a bit of ‘encouragement’ via a pipe and a mallet from outside back up the shaft tube, finally pushed the whole contraption free of the bulkhead & into the engine room.

The 1st photo below shows the SB out of the boat, fwd side, with one of the long push-bolts in place. The 2nd photo looks down through the SB while it was still in situ; if you zoom the photo, you may be able to make out the almost-worn-to-nothing rubber bearing fluting.

The 3rd photo shows the aft side of the SB, the tube behind the bulkhead, which contains a rubber bearing….already removed in this photo, to show the tube has a ‘lip’ to retain the bearing, which has to be inserted before the packing from the engine-room side.

The 4th photo shows the removed bearing and a retaining ring that sits between the packing and the bearing….this detail for the benefit of any OA owners and others with this unusual SB that may be faced with removal down the track. It seems that today, these SB’s are made only for shafts of 4” and greater. I’d guess that many are out there and have been re-packed regularly, with their owners oblivious to the rubber bearing that sits behind the packing space and which, while long-lived if the running gear remains undamaged, does eventually wear out and deserves replacement.
The SB will be completely cleaned up and a new bearing inserted tomorrow. I probably won’t be around to take a pic of the finished object unfortunately, but I’ll try to get the yard to do so.
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Old 07-27-2017, 06:31 AM   #25
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3rd & 4th photos per above post....
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Old 07-27-2017, 06:57 AM   #26
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OK, with shaft and SB sorted...almost....we struck an unexpected issue with the new props. As noted in earlier posts, the new props sit higher up the taper than the originals so the prop shop made up ~15mm thick bronze spacers, to go between the prop hubs and the locking nut. Photo 1 below shows one of the new props and these spacers.

But when the yard manager went to mount the Stb prop, he realized that the spacers wouldn't work with the original prop nut. The 2nd photo shows one of the old props with the prop nut sitting on top of it. This is a large domed nut and is the only nut used on the shaft: no smaller locking nut, no split pin to retain the nut. Instead, you can see a hole drilled through the dome nut flange, a set/grub screw goes through this hole & seats in a tapped hole in the original prop. We hadn't sent this somewhat unusual domed nut to the prop shop with the old prop and the yard manager and I hadn't been around to see this set-up when the original props were removed. Of course there is no hole thru the spacers and no tapped hole in the new props.

After a hurried phone consult with the prop shop, we have decided to drill a hole through the SIDE of the domed nut; fully torque it up against the new prop; and then drill a dimple into the shaft's threaded section. We'll then use a set/grub screw through the domed nut onto the shaft.

All this plus the work to finish up and re-install the SB will take another yard day....and I cannot hang around due to another commitment, so I'll have to leave it to the guys (they will likely be glad to see the back of me after all my hovering and photo-snapping!). I'll report back after I get back to the boat in a few days and make the 4 hour trip from the yard on Pittwater back to Aquabelle's home marina on Sydney Harbour.
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Old 07-27-2017, 07:00 AM   #27
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A better photo of the domed prop nut and its set-screw hole.
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Old 07-27-2017, 07:33 AM   #28
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Can you ditch the domed nut and go with either castellated nut or double nuts with cotter key?

Is the shaft standard SAE dimensions?

May still need a bushing but that is easy to make with a lathe from an old nut, etc.

Not liking the domed nut with a little lock screw.
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Old 07-27-2017, 07:55 AM   #29
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Eric...great to have your experienced eye on this. Yes, the shafts are standard SAE with 1:16 taper/ 2 1/4" od. We did talk about reverting to standard prop nuts (castellated or otherwise) but we'd then have to drill right through the shafts for the cotter pins. Only one shaft was pulled so that would involve pulling the second shaft (which has no issues) and the engineers at the yard said they'd have to send them off to a specialist shop as the shafts are too hard for their gear....so a lot of time/delay/cost.

I was surprised to learn the big dome nuts were fastened directly into the aft face of the original props (have you seen this done before?)...but it clearly worked for some 3500 hours of operation. I'm not sure doing much the same thing, but sideways and into a dimple on the shaft, is any less secure? The domed nuts are really substantial...the set-screw needn't be small.

I am not familiar with all the options for prop nuts; is there a set-up I could use that doesn't require drilling thru the shafts to take cotter pins?
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Old 07-27-2017, 08:06 AM   #30
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Is this an acceptable alternative to locking the prop nut on a larger shaft with 26 1/2" prop? Called a TAB WASHER & explained here: http://www.hamblepropellers.com/80735/info.php?p=9
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Old 07-27-2017, 09:08 AM   #31
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Tab washer should be ok. Should also be able to drill the cotter pin hole in the shaft while installed. It might be a tough SS, but it is not that tough. A good bit and proper cutting fluid and a battery drill should do it.

Domed nut may be fine, as it has held up for a long time. Just would rather see a very positive restraint should a nut loosen. Two nuts and a cotter are dead reliable.
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Old 07-27-2017, 05:11 PM   #32
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Ok I don't fully understand the risk in changing from a locking screw thru the domed nut's flange into the prop hub (ie along length of shaft) as was original; vs putting the lock screw through the side of the dome nut into a dimple recessed into the shaft thread (ie perpendicular to the shaft). I'm thinking of supporting this second arrangement with a tab washer & blue loctite to the nut's thread. Maybe at the next haul out I can get a pre-warned yard to drill cotter pin holes thru the shafts in situ. Sound like a reasonable approach?
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Old 08-02-2017, 06:34 PM   #33
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OK, I can now close out this project. Stuffing box was cleaned up and new/previously unknown bearing within it was replaced (it is only 3" long so was cut down from a 9" cutlass bearing). Box was re-packed with 3 rounds of 10mm GFO stuffing. Boat was splashed and with the engineers on board, I re-filled water tanks and the shaft coupling was mated to the transmission via a 'rubber' DriveSaver. Snr engineer wasn't wild about doing this work with the DriveSaver in place; said best practice was to remove the DriveSaver and insert a custom-made steel or aluminium 'filler' of same dimension. I wasn't willing to be without the boat for another week while this was done so I told him to do the best he could off the DriveSaver. In the end, he was satisfied with the alignment result he got and he stayed in the engine room while I took Aquabelle out for a gallop over a range of rpm's. He tinkered with the stuffing box while observing the shaft. No vibration, no run-out on dial indicator and no drips, with box remaining cool to the touch. Disembarked the engineering team and then did the 4hr run back to Sydney Harbour @ 1800rpm & 10kts. Stuffing box checked every 30min and remained cool and drip-free throughout. Some photos attached below.
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Old 08-02-2017, 06:39 PM   #34
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Good outcome!

I could not see any rudder or shaft zinc anodes - don't you use them?
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Old 08-02-2017, 06:42 PM   #35
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Eagle eyes Brian! I use shaft brushes immediately fwd of the stuffing boxes...they just hadn't been re-installed when I snapped the photos. I used to use conventional shaft anodes but after having them come off on one side once and only discovering it was missing when I went swimming beside the boat, I changed to the brushes. The rudders are tied into the bonding system internally.
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Old 08-02-2017, 06:47 PM   #36
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Interesting! I have shaft brushes and rudders bonded, but still use anodes. The anodes do dissolve so I think its good to have them. I don't know whether its caused by other boats in the marina are creating stray currents via their electrical systems or not. So I just replace the anodes when hauling for antifoul.
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Old 08-02-2017, 08:12 PM   #37
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The sparkie at my previous marina (Bobbin Hd) came aboard annually and connected up to the bonding system and then dropped the test anode over the side and took readings. Everything was always perfect post the shaft brushes. Haven't had that done at Cabarita (there's no resident sparkie) but now you've reminded me, next time I see a contractor-sparkie at the marina (a couple seem to be regulars) I might get them to do the proper test, just to be safe. Certainly a visual inspection of the below-waterline metals all looked good this haul-out, but one never knows without actually do the proper micro-voltage test. (nb: I do have 2 x big aluminium 'maddox' anodes on the transom to which the bonding system ties back; they last about 24-30 months)
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Old 08-02-2017, 10:03 PM   #38
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Late on the prop nuts but mine is very alike.
Domed bronze nut but has a hole, 5/8" , centred so a stub thread shaft can be run into a thread hole in the shaft end. Then two nuts are run onto the stub shaft a jammed onto the dome nut and each other for a lock.
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Old 08-02-2017, 10:26 PM   #39
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C lectric...thanks for that. I guess the 'stub thread shaft' goes through the nut, jamb nut and dome nut and then on into the tapped hole in the shaft centre...have I got that right? If so, I suppose a hole could go through that 'stub thread shaft' right after the last nut, to take a cotter pin...if one wanted to be belts-&-braces?


For me, I wonder if it would be easier for a yard to shallow-drill and tap a thread into the end of each shaft to take a 'stub thread shaft' vs drilling right through the shaft to take a cotter pin, with the prop shafts remaining in the boat? (Obviously all is easier to do if the shafts were out and at a shop...but I really don't want to pull shafts out of the boat if I can avoid it.)


But you have given me another idea. Why not just drill the centre of the dome nut as you have done and tap THAT hole (easy to do on the bench); screw in a threaded rod to where it butts up against the shaft end but without drilling into the shaft end; two locking nuts outside the dome nut as you have; and a cotter pin behind the aft nut to secure all? That would be easy to do....and I think would achieve a positive lock of the dome nut?
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Old 08-02-2017, 10:53 PM   #40
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All sounds complicated. Conventional pair of nuts does it for me.
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