Ron Welcome aboard-
Fellow-Ship gives some great advise. You can also tap the deck in various areas with the handle of a screw driver. If it is rotten you will know sort of a thud instead of a ding. The stringer should be fine if the deck is ok. The stringers are all glass. If the deck is rotten, which you should be able to tell with the tapping test I would be concerned about the stringers but Mr. Potter may disagree with me here because Seacraft re-engineered the stringers in the 20 in 1970 and from then on they were much more beefy than the ones in my 1969 which had issues after the deck rotted away and collapsed on them.
This is also a sure way to tell if there is rot [img]images/icons/grin.gif[/img] :
