Ok, I'll take a shot. crawl down into the lazarette. Look up there, and see what they are fastening.
I would bet they are a 'removed item' (grill table brackets, bait table brackets, just plain table brackets) OR are reinforcing blocks between the inner cockpit component and the hull to stiffen them both.
OR (in a long shot idea) were backing blocks for something mounted on the outside of the hull (davits come to mind) By looking up in the lazarette you could ascertain if there are any gelcoat patching runoffs dripping down from the hull side to confirm. I have about 40 of these little 'reminders' on my boat all over the place. It was done by previous owners, who then awlgripped over them all. So I have a hard time rationalizing removing them all to have dozens of patch jobs to highlight mine!
View attachment 76673
Here’s a representative of some of my darling screws on the long long list of things to patch.
Coincidentally, I have the same round 'vent' on that side, which was installed (I believe) as a way to have a hand access area to bolt on the outboard bracket on the transom. It IS accessible from the lazarette (Been there, done that.)