I use SS swivels with my galv. anchor and chains. Several (dock walker)
experts have tried to tell me I should have all galv. with the galvanic
corrosion as the argument.

If I could get a very streamlined galv. swivel that would go through my bow
roller, I would switch but only the SS will do that job.

Here is my reasoning. If anything deteriorates, it will be in the anchor
stock, where the swivel contacts it and on the first couple anchor chain
links.

I will watch both, but if I anchor a lot, I will have the anchor
regalvinized after a couple years anyway and I reverse my chain every year
and if it looks like the first couple links are loosing to much zinc, I can
cut that much off and be into fresh chain. No big deal in the overall life
of the chain..

To answer your other question regarding shackle strength. You can look up
your shackle up in some reliable publication or catalog and they will give
the various strength 'ratings'.. However, most shackles are now made
'offshore' and I would degrade them at least 25% just as a general
precaution.

My (other) recommendation is to use the largest shackle that will fit your
chain (pin through link) but still be small enough to go over your bow
roller and down you chain pipe (if your using rope/chain rode).


--
My opinion and experience. FWIW

Steve
s/v Good Intentions