Most of the boats had a davit there at one time, make sure there are absolutely no failing fasteners where that might have once been. Another place would be the screws down from the flybridge bench seating into the flybridge deck. There is at least one screw in the corner that could see some standing water as it drains from the flybridge. That need to be sealed for sure.
I don’t want to entirely discount the screws that are horizontal on the outside that attach the flybridge, but those are “horizontal” and typically would not have much water running through there. It certainly could leak, but not typically this much. They screw into the wood core in the side walls of the cabin. If you think that is in fact your leak, follow up questions I’d start with: do the screws still “take hold” and tighten or do they just spin such that there is no pressure and no longer have the ability to clamp/seal.
How about the wood just under the flybridge lip along the sides. Is it damp or rotting and showing signs of water running along it?
Putting new sealant on the screws is not terribly difficult, but you need to make sure that is in fact the spot leaking and also that the sealant can be captured and will be stable. It’s been awhile since I’ve had the 8 inch or so trim that the curtains hang within down, but I believe it gives visible access to where those screws are located. Might help to determine if that is in fact the leak and help assess whether the core is stable enough to hold a screw. If it is, I would reseal that hole. Actually since I’m paranoid about wet core, I’d probably over drill it, fill with epoxy, redrill the hole and then re-seal. You then need to solve why water is channeling through there and that’s probably because of a gap where the flybridge meets the deck on the inside. I’ve caulked that area before for that reason.
If there is any moisture in the plywood core, you really need to get it dry. If it’s mush, replacement. I can tell you that any core leaks will rot if left to fester and that’s not a fun job.
Is this a common area? Maybe not unheard of, but I would not say this is an area where many have had leaks. Windows would be way more common. A little water channeling behind the flybridge and an annoying drip onto the top of the door, yeah not unheard of. Coming through those horizontal screws, much lower on the list and why I’m hesitant to go there immediately without checking other causal factors along the way.
I’ve had my 1980 48 since 2006. I’ve kept it undercover and that makes a ton of things simply easier over time. Any screw that I’ve not personally pulled and re-sealed I just assume are leaking. Same goes for windows if you have not pulled and re-sealed. Ah….one more possibility, there is a rail Stantion base up there near that corner that could drip down…that’s a possibility too.