Buying a GRP yacht that has been sitting in warm Turkish waters for years? An osmosis survey tells you exactly what is happening beneath the gel coat — before you commit. We map moisture levels across the entire hull, grade any blistering, and give you a repair cost estimate in a single English report.
The Aegean and Mediterranean are warm. Surface water temperatures sit between 22°C and 28°C through the sailing season. That warmth accelerates the chemical process behind osmosis — water migrates through the gel coat, reacts with uncured polyester resin, and forms acidic pockets that blister outward.
A boat kept in Scandinavian waters might develop osmosis after fifteen or twenty years. The same hull in Bodrum or Göcek can show signs in eight to ten. Charter boats — continuously afloat, rarely hauled — are especially vulnerable.
We have inspected hundreds of GRP hulls across Bodrum, Marmaris, Göcek and Fethiye. The pattern is clear: pre-2005 hulls that have spent their lives afloat in Turkey carry a high probability of measurable osmosis. That does not mean the boat is worthless. It means you need to know the extent, the cost, and whether it has been treated before.
From haul-out to report — what happens during an osmosis inspection.
The boat is hauled using the marina travel lift. The hull is pressure-washed to remove antifouling and growth. We wait 4–8 hours for the gel coat surface to stabilise before moisture readings begin.
Using a Tramex Sea Surveyor capacitance meter, we take readings at a minimum of 40 points across the hull bottom. Results are plotted on a hull diagram showing dry, moderate and wet zones.
Any visible blisters are counted, measured, and — with the owner's permission — opened. The liquid inside is tested for acidity with pH paper. Blister depth and distribution determine the severity grade.
A written report with moisture map, photographs, severity grade and a treatment cost estimate is delivered within 24 hours. We include yard recommendations in Bodrum, Marmaris and Göcek.
Scattered small blisters, moisture readings 15–25%. Localised gel coat repair and barrier coat. Cost: €1,500–€3,500 for a 35–45 ft hull.
Widespread blistering, moisture 25–40%. Full gel coat strip below waterline, 8–12 week drying, epoxy barrier. Cost: €4,000–€8,000.
Deep delamination, moisture above 40%, structural laminate affected. Full peel, extended drying, laminate repair and barrier. Cost: €8,000–€15,000+.
Prices are indicative for Turkish boatyards. Actual cost depends on hull size, yard location and extent of damage. Treatment in Turkey is typically 40–60% cheaper than Northern European yards.
Absolutely. Osmosis is not a deal-breaker — it is a negotiation tool. If the survey shows moderate osmosis costing €5,000 to treat, that amount comes off the purchase price. Many buyers deliberately target boats with untreated osmosis because they get a lower price and then have the work done in a Turkish yard at competitive rates.
After gel coat removal, the laminate needs to dry to below 6% moisture content. In Turkey's summer climate this takes 8–12 weeks. In winter, it can take 16 weeks or more. The boat must stay on the hard during this period. Rushed drying leads to premature barrier coat failure.
A properly applied epoxy barrier coat — typically 5–6 coats of a product like International Gelshield 200 — dramatically slows water ingress. It is not a lifetime guarantee, but a well-applied barrier after proper drying can protect the hull for 15–20 years. The key word is "properly" — application over a damp laminate is worse than no barrier at all.
Yes. A focused osmosis and moisture survey costs €350–€600, while a full pre-purchase survey is €600–€2,500 depending on boat size. If the hull has already been surveyed and you only need moisture data — for example, to check whether a previous treatment is holding — the standalone osmosis survey is the right choice.
Send us the boat details on WhatsApp — length, location, and whether it is currently afloat or on the hard. We reply with a written quote the same day.
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