Limber Me Timbers

[osprey]

I keep getting water in the bilge after I launch my 89 23ft cc. It's dry when I launch and then when I haul out, I find 20-30 gal. in the bilge. Refitted the forward hatch drain thinking it was the culprit. Still water in the bilge. Pulled up the rear deck hatch to check for drains between the stringers (limber holes). None found. What the customer can't see, saves the company money.
So, I notice moisture weeping thru the woven roving at the base of the stringer both port and starboard and decide to bore a couple of holes. Yes, water came pouring out!! I enlarged the half inch hole I drilled with a dremel so I could get a feel for whats in there. Seems like it is just foam. Wet foam that is. Helps explain why my transom needs attention. My question is how thick are these stringers ? my drill bit is around six inches and it wouldn't hit the other side. I can guess that the bulk of my h2o problem lay on the other side of the stringer. Did they build these boats without any wood in the stringers? I would be greatful if someone could direct me to any threads on my problem or post a solution. I don't really want to chop into those babies unless I really have to. Thanks