How to tell if hollow stringers are bad? 20' 1969

[69Seacraft20]

I'm trying educate myself on seacraft hull frame construction. After doing some searching here I've found that my 1969 seacraft stringers are hollow. I'm not sure how they can rot.

If I were to remove my deck and inspect the stringers, what should I be looking for?

If they are not cracked or delaminating is it safe to assume they are fine?

Should I drill tiny (repairable) holes to check for water?

Thanks