So I’ve been looking at older fiberglass boats from the 70s and 80s lately, and I keep hearing about the whole issue with osmosis. I found one that seems perfect otherwise, but the survey mentioned a few small blisters in the gelcoat below the waterline. The seller says it’s minor and was treated years ago, but I’m just not sure how much of a red flag that really is for the long term.
osmosis worries me when I see gel coat blisters on an old boat. a few small pockets do not automatically mean the hull is failing but it is a sign to be cautious and to get a moisture check done
as a survey minded reader I want to quantify the hull moisture before we decide on any cure options. osmosis is not an instant wreck but it can grow with time
if the seller swore the problem was fixed years ago do you have a recent moisture reading or a record of repairs to confirm osmosis history
i am a bit skeptical about confident answers from sellers on osmosis the truth is a good survey can reveal much more than promises
it may help to reframe the issue as a hull health one not only osmosis the gel coat and laminates behave differently in aging boats and the risk comes from hidden moisture paths
practical steps for a boat with possible osmosis ask for a moisture meter reading core sample and a professional opinion before any sale the goal is to see if there is a stable path forward