150 ft yacht with 130mm shafts. Problems with shafts. 2

[captstaats]

Hello Everyone,

I am new to this site and could really use some information. I have two shafts 130mm with heavy pitting that I need to have resurfaced and machined. I am probably not using the correct terminology please bear with me. Some of the pitting is 1/2" deep but I have heard that the shafts can have a new surface applied through a welding process and machining. Is there a depth of corrosion that decides when it is time to scrap the shafts? The yacht is in Miami,FL, if someone knows of a reputable machine shop that can handle this type of job please let me know. Or if I am missing important information about the process I am all ears. The spots in question are between two bearings. Please see the attachment for a picture of the corrosion.

 

[MikeHalloran]

Nice boat.


Mike Halloran
Pembroke Pines, FL, USA

 

[tbuelna]

"Nice boat."

No kidding! I just took a look at the website for this boat (or "private estate" as described in the brochure), and it does not look like the owners are hurting for money to pay for repairs.

The cost of machining a new pair of prop shafts from a premium material like Aquamet 25 would probably be less than $40K. Which seems like a relatively modest expense compared to the cost of paying salaries of the Golden Compass's ten crew members.

 

[msquared48]

Where were the sacrificial zinc anodes, or were there any?

Mike McCann, PE, SE (WA)

 

[tbuelna]

In the first picture posted above you can see a MIG welder sitting below the corroded prop shaft. I hope they weren't using the MIG welder to rework the corroded sections of the shaft in-place. 17-4 stainless can readily be welded, but the shaft would need to be heat-treated after welding, re-machined/straightened, and balanced.

 

[DekDee]

tbuelna,
Looks more like an SMAW welder to me.
What makes you think it is GMAW ?
Cheers,
DD

 

[captstaats]

Very observant guys. The welding machine is being used for hull plating replacement. The shafts are at F&J Propeller in Miami. They will be machining and welding the deep intrusions and buffing back down on non bearing surface. See attached pictures of test area. They will be doing an overlay on the bearing and packing surface. They have a 50 ton press for straightening the shafts. Thanks again for all of the input.

 

[captstaats]

BTW- There were no anodes on the shafts. The had a bonding rider on the shaft but that is it. Will be investing in 130mm ID zincs. Anyone know a good place to get the zincs at wholesale?

 

[tbuelna]

...Looks more like an SMAW welder to me. What makes you think it is GMAW ?

Definitely a Miller machine based on the blue paint. The only reason I assumed it was not a stick welder is because there are three cables attached to the machine face.

Also, if you look at the second photo in the post above from captstaats, you can clearly see the remnants of a piece of errant MIG wire just to the upper left of the weld repair.

 

[kingnero]

Was there any NDT performed? As I see the repair, I wouldn't OK it. I'd like a bit more certainty than just a visual inspection on those shafts. I would also be hesitant on using GMAW/MIG for this type or repair.

 

[EdStainless]

A piece of wire and a lot of oxidation.
And what about all of the little pits? Those need to be done away with also.
What material is being used as weld filler?

Looking at the boat specs it says that the engines are 750hp. That makes these very low strength shafts.
Which is good news, since the repairs will not be highly stressed.

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P.E. Metallurgy, Plymouth Tube