sctpc said..Pulled the mooring up today,
chains getting a bit thin around the wheel there
Why do you not get rid of the chain altogether and splice up a loop of line of sufficient strength with irrigation hose anti chafe on the loop and the loop of sufficient size to go through the weight and be looped back through itself and cinched up tight??????
The mooring contractor will give you all sorts of reasons why you should not do this because it will put him out of a job.
The set up I have described will last a lot longer than the chain which is really only good for about three years.
The set up I described can also be replaced by a diver armed with a knife in less than an hour and does not require lifting of the weight and subsequent repositioning.
Lay flat irrigation hose is very tough material. Farmers lay it all over their farms and drive over it with their vehicles even when the hose is on ground where there are pebbles and all sorts trying to punch holes in it.
I like your mooring weight by the way. It appears to be two railway wagon wheels concentrically attached to each other. What does it weigh?? Looks to be no more than 300 kg to me.
Note how the wagon wheel still has paint sticking to it and the edges of the centre hole are shiny yet the chain is well and truly on the way out. That is because the wagon wheel is cast steel and therefore a more base metal than the forged steel chain. So not only is the chain subject to sacrificial electrolysis, it is also subject to chafe from sand etc and wear at the links.
If you use 3 Strand Superdan Rope, made to AS4142.1993 you will find it has more than twice the strength of equivalent diameter Silver line and a lot easier to work in splicing. See www.samallen.com.au or phone Brisbane 07 3902 7222. It is not much more expensive than Silver line but a world of difference in quality.
If you sheath the splice loops with the irrigation hose, bottom and top, you will get many years of service from it. An annual dive on it for an inspection report is not going to cost you a lot of money and should suffice from an insurance point of view.