Hi, I put my stainless steel eye bolt in at the end of April 2016. Since then the boat has probably actually been in the water about a month and a half out of the eleven months. I took the eyebolt out last weekend (end of March 2017), It came easily and felt very smooth when unscrewing.There was no damage to the threads, but there was some black 'dust'. I couldnot check the state of the thread cut in the top of the keel, and I am afraid I cannot remember whether I put grease or silicon on the threads when I installed. I have put it back with marine silicon on the threads. I have a photo which I will try and post.
[img=https://www.flickr.com/photos/the_hammys/33621205322] [/img]