Hull Blister & Osmosis Repair•Tampa Bay, Florida
Blisters are a sign of water working into the laminate. We open, dry and repair them, then seal the bottom so they don’t come back.
Osmotic blisters form when water passes through the gelcoat and reacts with the laminate, building pressure that lifts pockets of gelcoat or glass. A few shallow gelcoat blisters are a cosmetic issue; blisters in the laminate itself weaken the hull. We test and open a sample to find out which you have.
Shallow blisters opened, cleaned, filled and faired.
Gelcoat blisters are small, scattered bumps that sit only in the finish layer while the laminate behind them stays dry and solid, often on older or poorly cured gelcoat. We open a sample first to confirm they haven’t reached the glass, then grind each one open, let it dry, fill and fair it, and barrier coat the bottom.
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Widespread blistering treated across the whole bottom.
When blisters cover the bottom, water has worked through the gelcoat over a wide area and reacted with the resin, often leaving an acidic, vinegar-smelling fluid inside. A moisture survey tells us how deep it goes, then we repair the blisters or peel and dry the bottom, rebuild damaged glass and finish with an epoxy barrier coat.
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Deep blisters in the glass repaired with structural laminate.
Blisters that reach into the fiberglass weaken the bond between layers and can grow into delamination. We grind them out to sound, dry laminate, replace the damaged glass and fill the voids. Below the waterline we repair with vinyl ester, or with epoxy when the boat can’t stay out long enough to dry fully.
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Gelcoat removed and the laminate dried before rebuilding.
A full peel is only needed when blistering is widespread or deep and moisture readings are high across the bottom. With the boat hauled, the gelcoat is ground off the whole bottom and the laminate is washed and left to dry, with readings taken along the way. Rebuilding starts only once the laminate is dry.
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Multiple coats of epoxy barrier to stop water getting back in.
Blistering happens when a bottom sits in the water with no barrier coat to keep moisture out of the laminate. Once the repairs are done, we apply several coats of epoxy below the waterline to slow water getting back in. It’s the layer the hull was missing, and it goes on whichever resin the repair used.
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Faired smooth and prepped for bottom paint.
Ground-out and filled blisters leave a bottom uneven, and bottom paint shows every high and low spot. We fair the repaired areas into the surrounding hull until the bottom is smooth and true again, so once it’s sealed it’s ready for bottom paint and looks even rather than patched.
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Moisture readings and sample blisters show how deep and widespread the damage is.
Blisters are ground open, washed and the laminate left to dry fully.
Damaged glass is replaced and voids filled with epoxy and fiberglass.
Faired and sealed with an epoxy barrier coat, ready for bottom paint.
A handful of blisters can become hundreds. Left alone, osmosis keeps drawing water into the laminate and the repair grows with it.
Blistering on a hull bottom is hydrolysis: the laminate sits in constant contact with water with no epoxy barrier coat to keep it out. Water works through the gelcoat, reacts with the resin, and the pressure lifts the skin into blisters. Left unrepaired they grow in number and in size, and the bottom of the hull gets weaker.
Which resin a bottom is built from, and which one it is repaired with, decides how well it resists the next round. Three resins matter below the waterline.
What most fiberglass hulls are built from. It is the economical choice for production boatbuilding, and the one most prone to blistering when the bottom is left without a barrier coat.
Far more water-resistant, at roughly twice the price of polyester. A few builders lay up the whole hull in it; others use it only as a skin coat, the first layer of laminate behind the gelcoat. Fiberglass swimming pools follow the same pattern. It is what we use for blister repairs below the waterline.
About twice the price of vinyl ester again. We use it when a boat cannot stay out of the water long enough for the repair area to dry out fully, which a vinyl ester repair needs.
Whichever resin the repair uses, the bottom gets an epoxy barrier coat afterwards.That is the layer the hull was missing in the first place, and it is what keeps the water out next time.
Real repairs. Real results. A few blister and bottom repairs we’ve completed across Tampa Bay.
Blisters opened, filled and barrier coated.
Damaged glass replaced and faired.
Faired smooth and sealed.
Blister repair starts with a moisture survey and opening sample blisters to see how deep they go. Blisters are ground open and washed, and the laminate is left to dry — for widespread osmosis, the gelcoat is peeled from the whole bottom. Damaged glass is replaced, the bottom is faired, and multiple coats of epoxy barrier coat seal it against future water.
Seeing blisters at haul-out? Have them sampled before you paint over them.Painting over blisters hides them; it doesn’t stop them.
Based in Largo, Florida, we proudly serve boaters throughout Pinellas County, Tampa Bay and surrounding areas. Our fiberglass repair services are available at our shop or through our fully mobile service.
Water slowly passes through the gelcoat and reacts with chemicals in the laminate, creating pressure pockets. Warm Florida water speeds the process up.
Shallow gelcoat blisters are mostly cosmetic. Blisters in the laminate weaken the hull over time and should be repaired.
Only for widespread or deep blistering. Many boats just need individual blisters opened, repaired and a barrier coat applied.
Several coats of epoxy applied below the waterline to slow water getting into the laminate. It’s the key to stopping blisters coming back.
No — the boat has to be hauled and the laminate dried. We can haul and store your boat at our Largo yard.
Most of the time is drying. Small repairs take days; a full peel and dry-out can take weeks. We give you a timeline after the survey.
Let Captain Levi’s survey the bottom and recommend the right repair.
Have hull blisters you want looked at, need a quote, or ready to schedule? Fill out the form or give us a call — we’ll get back to you as soon as possible. Your boat deserves the best, and we’re here to make it happen.
Tell us about your boat and the damage. We’ll get back to you quickly.
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