When you are not sailing with the boat sitting in the water and not raining, I bet it is bone dry. However when you have people on board standing in the rear, sailing, motoring and so on, water is seen. Look at the bilge area under the rear berth and look at the aft wall separating the rear behind the rear berth wall. Then take a flashlight if you see a stream of water and following it back to the transom area. If so it will be one of two areas either the lower gudgeon or the part bolted on that holds the lower rudder pintel and if not, look at the hull to deck joint which most likely that is it. Then report back here and advise. I bet the marine putty after all these years needs to be repaired between the hull to deck joint at or below the water line which is why I said the above when in use or weight in the cockpit. If not, then I will advise plan b but if it is what I think it is then not a problem to fix. I can advise on that one.
