I had another guy interested in the boat who was going to buy it as is but backed out. oh well, I'm beginning to realise that boat selling isn't terribly easy.
I've had a close look at this "osmosis" too.
yes there are a few blisters and when you crush them there is some moisture behind them, but it doesn't smell.
The blisters do appear to be in the gel shield not the gelcoat too. The surveyor has not actually scraped back to the gelcoat when testing and hasn't actually popped any blisters himself as far as I can see.
I've considered getting the boat surveyed again and seeing what they say but it's all just more expense. Frankly I've dropped the price so low now that I don't get much out of it if I sell and any effort in doing work on her doesn't seem worth my time.
She is a cracking boat, she has looked after me well over the years and really doesn't deserve this ignominy.