Gunwhale mouldings often leak
I had that same problem on my 222 a couple of years ago, and I Talked to Rudy about it. He said that most likely, water was leaking in from the coaming. He was right. He said that the caulking under the moulding is only good for 8 to 10 years. I found out later that it can be good for less if you use any type of Fiberglass cleaning agent that has Oxcalic Acid in it. For example, one of my boating books tells their readers that Zud Cleanser, which can be perchased in any grocery store, will clean fiberglass,-- and it will. What they fail to say is, that it will eat out the caulking on your deck. I can only tell you how the mouldings were installed on the 222 because I've never looked at the 25, but the Rubber strips come together at the stern of my boat, and each strip has a screw to hold it. I took out these screws and removed the port gunwhale rubber from the aluminum moulding to a point where the other moulding butts up to it, which was somewhere near the bow. I then unscrewed the moulding strip and removed it. I cleaned the fiberglass surface, and recaulked it, and reinstalled the moulding and the rubber that fits inside it. Then I did the same thing to the other moulding on the starboard side of the boat. I used a regular high grade boat caulking. I wouldn't advise the use of silicon. You'll want to be able to remove this moulding again some day, so you need to stick with a regular caulking. I think that you'll find that, some small screw holes under these mouldings, are the culprit. If a leak persists, you're going to be able to narrow the problem down to a deck fitting like a stanchion or pad eye, a lot easier. Check out this web site and click on to "Tools and Techniques". I think you'll find the answers that you'll need about what type of caulking to use. Good luck!