I don't think replacing them with same size threaded rod is the best plan ... I think dumping the wooden rails is the best plan.
Or as a compromise see if you can go up a size without compromising an old piece of wood.

I have done two boats with SS rails and feel way safer than relying on these rinky dink long bolts from 30 years ago ... if one broke ... i am pretty sure the rest are showing signs of pitting as the photo indicates.

for some reason I kept the four best ones removed from 505 four years ago ... they all are pitted. I didn't have a problem with the wood rails until I ended up with a 225+ plus crewman when he was trying to put a reef in off shore. and then subsequently the pins started to break on 526.

[Linked Image]
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J30 handrail pins.jpg (43.72 KB, 2119 downloads)
hand rail bolt pitting prior to failure

Last edited by Cap'n Vic; 12/01/11 09:14 PM.