Deck fittings - One for the engineers:

[doug748]

My little boat (21ft) came with a similar fitting on the bow for attaching winch for winching onto the trailer. I used this fitting as a primary mooring attachment and it failed after a few years. The point where the bulky U bolt is cut down to 1/4 inch thread is the fail point. I replaced it with a 5/16 sized saddle with ordinary 5/16 bolts. This has survived many years since . Despite the fatigue producing sideways and tug loads. I would not use that fitting. ol'will

Spot on. I had not looked closely at the thing before I posted. Both ends have been turned down and then threaded, there is no sign of a radius to relieve the stress riser which falls exactly at deck level.
It's a low strength effort probably fitted new for the spinnaker pole downhaul (which is what the block is for) and pressed into service for the removable forestay.

Here is a close up (The apparent corrosion was a bit of discoloured mastic):



It's not up to the job.

 

[Tranona]

Sadly these tasks grow like Topsy - but you need to think of a complete and compatible package.

Jonathan

Don't I know it. Had similar problem finding the right U bolt for my cruising chute furler attachment - which is why I ended up being a nerd on the subject of U bolts. The only thing "standard" now seems to be thread size with other key dimensions - leg centres and length varying according to manufacturer. Baseline had the right one for me but postage was 50% of the modest cost!

Good dinner party subject, but if you used it for small talk you would not get asked back.