Sounds either it was coated with expoy and water migrated in or if glassed, which probably not, has been damaged and water again got in. The surest way to make sure is to have a marine survey. Depending where you are would drive the cost. If I was going to have a survey would need someone that has experience working on boats professionally rather than a match book cover degree. You could try The Society of Accredited Marine Surveyors, Inc.® - (SAMS®)
for someone in your area.
On the other hand, if you are getting a good price. Talk to a boat yard that and see what they say.
When I go, let it be by boat, with a steady breeze on the Chesapeake with a bottle of 7-up, a bag of ice, a plastic cup, and a box of wine