Should a person be concerned about the age of an older fiberglass (1977) boat even though it looks clean? Does old fiberglass get weak? The boat has only been in freshwater.
Sometimes it can become brittle especially where the seams have been glued/repaired. Problem is you sometimes dont know how well the former owner did any patch repair. My brother in law had an older bass boat come apart in the bottom and only had several minutes before it sank and he had to swim for shore. A good inspection of the boat first can more than likely show any problem area. Dont be afraid of the older boats, just inspect all of the seams for any possible weakness.
imho, the wood is not the problem, the negligence of the previous owner, and lack of proper maintainance is the problem. causing the wood to be the problem.