I have an older J-30 with the same moisture issue you describe on the starboard side of the hull.

Postings other places on this site indicate that the primary source of this moisture is from the engine exhaust.

I have had the area around the exhaust tube rebuilt and also have had the worst area of my hull where delaimation had begun (starboard stern quarter) re-cored.

Two questions:

1) What areas of mosture intrusion into the core did you identify, if any, other than the vermiculite/bilge line ?

2) Since I am not re-coring the entire starboard side of the hull would barrier coating be of any value? Since there is moisture in the core, isn't it almost certain to get into the laminate even if I barrier coat?