Broken Swivel

[Tinosa]

Looking for opinions on why this swivel parted…

Have a small mooring in about 4 feet of water I use for a dinghy or for temporary parking of small boats ~20’ that stay for a day maybe overnight. I would say this summer there was a boat on this mooring max 3-5 days and never in rough conditions. Mooring is in a well protected cove with significant breakwater in New England

Mooring is a 150lbs mushroom with 10’ of 5/8” chain with a top chain of 10’ 1/2”. Mooring ball and 8’ pendant. All gear new in 2014 so this was the end of its 3rd season. (inspected prior to each season)

I picked the chain off the bottom recently and all I found on the end of the chain was half of the swivel. There was no boat on it at the time... last used at least a month previous. See picture…

I have moorings with boats on them continuously for a north east season that don’t show this much wear and have certainly not parted. Any thoughts... anyone experience this before?

[Sailmonkey]

The swivel looks well worn, like the bolt head sanded its way through the lower half of the swivel.

Does the swivel lay on the bottom?


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[Hydra]

When I had my boat on a mooring, the galvanized-steel swivel failed because I put a stainless thimble close to it: galvanic corrosion occurred.

Alain

[GordMay]

Greetings and welcome aboard the CF, Tinosa.

[UNCIVILIZED]

Corrosion? Poor quality steel, thus accelerated corrosion? Malicious mischief? Halloween was just a few days ago

[Tinosa]

yeah i was thinking corrosion as the rest of the gear looks almost brand new, including the ring on that swivel... something like the bolt was mistakenly a dissimilar metal?

I worked on some conspiracy theories for foul play but it would have been easier to just pick everything up and drag it off... and leaving it in shallow water wouldn't prove much. Its easy to recover.

Now i was thinking if someone wrapped it in their screw would it be possible to twist in a way to get enough lateral force to snap the other side of the swivel...

anyway it seemed odd that a mooring without much use would wear so much... and no other gear looks worn.
cheers

[zeehag]

swivel is weakest link in your mooring system. i will not use them. i have watched and assisted as too many parted and boats required saving from disastrous spontaneous walkabout.