Cabin Sole damage

[cadteach]

I own a early 80's Islander, and I've developed some softness in my cabin sole, on the port side near where the stove would be (previous owner removed it). I've never seen water there, but it could be coming from underneath some how? Potential culprits include the engine bay, near there but more centered, but occasionally the bilge drain plugs and any packing drips build up. Could also be coming from port side windows, although it's a fixed window, and I have never seen any water marks, could it somehow go behind and end up underneath the floor? I've seen some water marks from the chainplates, but they are quite far forward of this area, and again, I've never seen water, just marks. However, we use it as a daysailer and were not on board if it's raining or wet outside.

I guess I'm asking for advice on determing the culprit and also repairs, can I inject resin or do I have to cut out the old and replace it. It's a small area, one board width and about 12 inches wide.

First boat I've owned, and we've only had it about three years, Thanks.