jib and spinnaker blocks

My friend recently purchased 909. The jib blocks are mounted on wood blocks on the rail of the boat. There is another block of equal size mounted to the side of the jib blocks for the spinnaker. We are interested in removing the second block and converting the jib to seat mounted blocks.
Our problem is that we can't seem to separate the two blocks. It looks like it is a single screw, that if it were removed the two blocks would separate. The screw comes out about half way and then continues to spin, but will not come out to release the other block.
Any ideas would be appreciated.

Thank you
John

Early Scots have nuts under the deck on the blocks. Later, they had self tapping screws. I think Dee at the factory told me that the method changed around boat 4000.

If you check with Harry or Dee, or the crew at the factory, they can tell you how to remove them.

Phil Scheetz
FS 4086