Gelcoat Blisters: Discount or Deal-Breaker?
Almost every older boat that has lived in warm water has some. The question is how deep, not whether.
By Boatmere Brokerage Desk · Updated · 7 min read
Pull an older boat that has spent fifteen summers afloat in Florida and you will probably find blisters. This is so common that a hull with none is more remarkable than a hull with some.
The useful question is never whether there are blisters. It is how deep they go.
What blistering actually is
Polyester laminate is not fully waterproof. Over years of immersion, water migrates through the gelcoat and reacts with unreacted material in the resin, producing a solution that draws in more water. Pressure builds, and the gelcoat lifts into a dome.
Pop one and you get a small amount of fluid that smells faintly of vinegar. That smell is the giveaway a surveyor is looking for.
Warm water accelerates it. So does staying in the water year-round. This is why a Great Lakes boat hauled every October at forty years old can be clean, while a ten-year-old Miami boat is peppered.
How surveyors grade it
Roughly three tiers, and the language in the report matters.
Cosmetic, gelcoat only. Small domes, shallow, scattered. The laminate underneath is dry and sound. This is a maintenance item and a modest negotiating point, not a structural problem.
Moderate, into the skin coat. More numerous, deeper, some interconnected. Moisture readings elevated in patches. Worth a real discount and a plan.
Laminate involvement. Widespread elevated moisture, blisters that go past the gelcoat into the glass, delamination on a sounding hammer. This is the one to walk away from unless the price reflects a hull that needs a five-figure intervention and several months out of the water.
Ask your surveyor to give you moisture readings as numbers across a grid, not as an adjective. Adjectives are how expensive surprises are described in retrospect.
What the repairs cost
Individual repair. Grind out, dry, fill with epoxy, fair, barrier coat locally. Sensible up to a few hundred blisters. Call it $40 to $80 per blister in yard labour, which is why the count matters more than the size.
Full peel and barrier coat. The bottom is peeled back past the gelcoat, the hull is dried, faired, and given multiple epoxy barrier coats. $250 to $450 per foot in 2026. On a 38-foot boat, $9,500 to $17,000.
The cost people forget is time. Drying a saturated hull takes six to twelve weeks, sometimes a full winter in a humid climate, and you are paying yard storage throughout. A peel job agreed in March is often a boat you get back in July.
My actual view
Buyers over-weight blisters and under-weight moisture readings.
Blisters are visible, alarming and easy to point at during a negotiation. Elevated moisture across a transom or a cored hull section is invisible, far more serious, and gets a single line in the report.
If I had to choose between a hull with two hundred cosmetic blisters and dry readings, or a smooth hull with a wet transom core, I would take the blistered one without hesitating. One is a weekend of grinding spread over a couple of seasons. The other is structural.
So use blisters as a negotiating lever, by all means. Just make sure you are reading the rest of the report as carefully as you are looking at the photographs.
Frequently asked questions
- Are hull blisters a deal-breaker when buying a boat?
- Usually not. Small gelcoat blisters are cosmetic and common on older boats kept afloat in warm water. Blisters that penetrate into the laminate, or a hull with elevated moisture readings across large areas, are a different matter and justify walking or repricing heavily.
- How much does a bottom peel and barrier coat cost?
- In 2026, roughly $250 to $450 per foot for a full peel, dry-out, fair and barrier coat. On a 38-footer that is $9,500 to $17,000, and the dry-out period alone can run six to twelve weeks depending on climate.
- Can you just grind and fill individual blisters?
- Yes, for scattered shallow blisters. Grinding, drying, filling with epoxy and recoating is a fraction of a full peel and works well when the count is low. It stops being sensible somewhere around a few hundred blisters, where labour exceeds the peel cost.
- Do blisters affect a boat's structural strength?
- Gelcoat-level blisters do not. Blistering that has progressed into the laminate can, because it indicates water has reached the glass and started breaking down the resin bond. That is what a surveyor is checking for with a moisture meter and a sounding hammer.
