I am sorry to write this because I think you'll feel bad about it, but it looks to me as if you've got water
intrusion under at least the forwardmost screw holding that chock on, and quite possibly, the aftmost one, too. You'll need to remove it and discover what's going on under it. You may have some rotten timber to remove, too.
There are people here on CF who can talk you through it, if there's no shipwright in your area who understands timber.
Anyhow, after you've discovered what's happening with your hull
joint*, then 5200 (which turns slightly pink) or 4000 are both excellent sealants, but the 5200 is the stronger glue, which should not be used if it's something you will want to remove.
* Now is the time to see if the water
intrusion has come below, as well. A friend with a Cheoy Lee
similar to yours, it had come in and damaged the attachments of the bulkheads to the deck
, and repair was a big job. So it really needs a thoughtful evaluation.
Good luck with it.