Old fiberglass boats
 

I'm thinking about buying an old 1984 Formula (restored) fiberglass boat. It looks mint to the naked eye, but how can you tell if it has any rot underneath the exterior beauty of the boat, besides looking for soft spots on the floor of the cock pit, and the stern, (it is an inboard), or just "banging" around the hull with your hand so to speak? I have heard that Formula has no wood in their hulls, (all fiberglass), but if this is true, I don't know what year that started, or if they have always been built that way. I have gone on Formula talk forums, but have had no luck to this question. I will call a Dealer if need be, but don't want to waste their time with a "stupid question" at their busiest time of the year. Thanks in advance with any tips to look for.

I don't know Formula's so not sure if they have wood stringers or not, my guess would be yes for 1984. If so, just banging around the floor won't tell the story. You need to get to the stringers and can do small core samples to test the condition. Some will tell you to just turn the engine mount bolts, if they snug up the stringers are in good condition. this may be true for that particular spot, but really more investigation is needed if you really want to know the condition. A marine surveyor could be hired to really give you a report on the boat, that would be the safest way to go.

Get a marine surveyor who emphasizes old fiberglass boats in his practice. Surveyors list their specialties on their websites. A surveyor can also tell a lot about the fiberglass moisture content, engine-compression, oil analysis, etc. and look at all other systems. A surveyor would normally want to see the boat out of the water as well as conduct sea trials.

This may be overkill for a 30+ year old boat, priced at a few thousand dollars.

Talking to a dealer is probably worthwhile. I wouldn't worry about how busy they are at this time of year. If they can't help you, they'll say so. Otherwise, I'd expect to pay them for an hour or two to do a compression check and inspect overall.

Getting service records from the seller may be beneficial.

Same answer for any used boat purchase: hire a surveyor.

When we bought our current boat the credit union required a marine survey before finalizing the loan. We used Mark Corke out of Maine, and he was quite responsive and thorough.