Just how bad are these keel bolts?

[GrahamM376]

It looks as though the studs and nuts are the usual Medium carbon steel used by the French manufaturers. If so they rust very easily and can look very much worse than they really are, I have pulled some that looked absolutely past it, only to find the bit that did the work to be in fine fettle. Pulling and inspecting the bolts/studs is usually managable one way or another. The studs can sometimes be pulled by double/treble nutting and using a blooming great lever arm on the spanner/socket/stilson. A blob of weld on top of the nut and stud works well if the double nut fails. Make sure the boat is on the hard first though QUOTE]

I agree, they usually look worse than they are. The ones on our last boat looked much like those so I hammered an undersized socket on and removed the studs and nuts complete. All threads were in perfect condition below the nuts and backing plates, although the nuts couldn't be removed "upwards" due the rust buildup on the studs. The ones on our current boat also look the same but they're staying put. No sign whatsoever of keel movement.

 

[Modulation]

I had a surveryor poke around this morning. His view was (as advised by some on the thread) that it was nothing to worry about. The front and back bolts are both fine, which would likely show the most damage if the boat had been badly grounded. His view was that the corrosion around the centre bolts was due to the bolts being sealed in with gel coat, causing the rust to expand and crack the surrounding gel coat. His advice was just to clean them up, treat them with an anti-corrosion compound, and leave them exposed to the air.

Interesting. The keel studs on my 20 yo Ben looked a lot worse than the op's photos and I'd resigned myself to replacing them. Anyway when she had her mandatory 20 year insurance survey I specifically steered the surveyor to have a close look. After a few minutes of poking around he said that they were fine - just looked terrible. His written survey confirmed this.
Unconvinced, I drew one of the smaller bolts and guess what? Beyond the exposed hexagon it was like new!
So no new studs after all