In preparation for the new season we decided to overhaul Bonita's mooring. The mooring chain is mostly out of sight on the river bed and when you haul it up its all covered with thick mud and rust, so its difficult to know just when it needs to be replaced. Better too soon than too late: it hadnt been done for several years. Various elements need to come together for this operation to go well: a good low tide, calm weather and plenty of help. I had Geoff, Allan and John on the job and it all seemed to reasonably well. I have tried to refine the process over the years and a fairly recent addition is a portable 12v electric winch which definitely makes the whole process quicker and easier.
Often you find that much of the chain is in reasonable condition, but there is a greater degree of deterioration in the galvanised shackles joining various parts of the mooring together. The weak point in the shackle is the thread which holds the pin in. We secure the pins with wire and cable ties, but even so, once the thread has corroded away, the pin becomes loose and the shackle is unsafe. A shackle with metal thickness of perhaps 12mm will have a thread holding the pin in place where the metal may be just 1mm thick. Many shackles get thrown away when they are 90% intact, but just the thread has rusted away, as with this one below...
I have tried dipping the shackle pin in grease or glue to try to prolong its life, but neither seem to make much difference. The answer, I have found, is paint. Dipping the shackle pin in an oil based paint - any colour will do - before tightening it up prevents the water getting into the thread and enormously prolongs its useful life.
So I still worry about Bonita on her mooring in the Swale when the named storms sweep in, but I worry a bit less knowing that the chain and mooring gear is, if not new, then at least fairly recently inspected.