I think the level is about 15%. Any wetter than that and they'll definitely rot.
There's usually more than one wetness point. If the manufacturer missed one sealant point, they probably missed more. There's really no such thing as "dry out" on fiberglass-encapsulated wood. If the water saturated the wood thru something as small as a screw hole, the wood wil be rotten crumbles before the moisture escapes the way it came in.
Moisture meters tend to be a bit of voodoo sometimes. A lot depends on model, calibration, the weather and whose using it. Having just had a boat surveyed, I've been through it. What's high or low can be REALLY subjective....some boats come right from the factory and can show up to 15%. If he's telling you there's a problem, I'd say a survey is definately in order. If he finds an issue with it, best bet is get it looked at by a reputable glass guy before making the purchase. With the market the way it is, you can definately set the terms of sale in that regard. While they can't to anything invasive pre-purchase they should be able to tell you whether it's likely a $500 repair or a $5K repair. the boat I bought was 500 miles away. When I "described" the damage found during survey to my glass guy...it was an $1K job...once it got up here and he could eyeball it...turned out to be a 3K job....all from a 1" crack. Be sure to proceed carefully.
