Gelcoat Crazing

By Don Casey

Revised by BoatUS editors in April 2012


If the surface of your boat looks like a cracked eggshell, the gelcoat is suffering from crazing (sometimes called alligatoring). The easiest repair method is to sand the surface heavily and roll on two coats of epoxy primer followed by two coats of two-part linear polyurethane. The epoxy fills and seals the cracks, and the polyurethane restores the color and gloss.

If you don't want to use paint, you can grind away most of the crazed gelcoat and replace it with a fresh application of color-matching gelcoat paste. What won't work is to "paint" over the crazing with new gelcoat. The gelcoat will bridge the cracks rather than filling them, and the crazing will soon return.

By the way, localized crazing (as opposed to all over the boat) is almost always due to flexing of the underlying laminate. In this case, you must stiffen the affected area before you can successfully repair the crazing. 

Don Casey has been one of the most consulted experts on boat care and upgrades for 30 years, and is one of the BoatUS Magazine's panel of experts. He and his wife cruise aboard their 30-footer part of the year in the eastern Caribbean. His books include Don Casey's Complete Illustrated Sailboat Maintenance Manual, and the recently updated This Old Boat, the bible for do-it-yourself boaters.


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