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The Smart Buyer - How to tell if that core is wet

Let’s say you’re in the market for a used powerboat. It might be a center console, a dual console or a walkaround from the 1970s or ’80s. Many builders back then used plenty of wood to core the stringers and transoms of their boats, so you’ll want to find out if the cored material is wet, which compromises the structural integrity of the hull.

Is there a relatively simple, quick way to determine if the core is dry and strong or wet and weak? Yes, says Jeff Perette, a fiberglass repair specialist and owner of East Coast Fiberglass in Marshfield, Massachusetts (eastcoastfiberglass.

com). When Perette inspects the laminate of a boat, he takes two tools with him: a moisture meter and an architectural hammer. “Your average Joe probably doesn’t have a moisture meter, but you can get an architectural hammer at just about any hardware store for about $10 to $15,” he says.

He uses the hammer to perform a simple tap test on the laminate in question. “I walk around the boat and tap different areas — key areas like the transom — and I listen carefully,” says Perette. “I’m listening for contrasting sounds. A dry core with a solid laminate gives off a clean, crisp sound when you tap it. When you tap an area with wet core, there is a real deep, deep sound, like you’re banging on something that is hollow.”

Greg Group, a longtime surveyor and the owner of Great Lakes Marine Surveyors in Mentor, Ohio, also listens for specific sounds when tapping. “It might sound overly simple, but a solid laminate sounds solid. It sounds firm, with a rap, rap, rap,” says Group. “If you’re hearing a deep thup, thup, thup, that’s bad.”

For a small boat, a simple tack hammer will do — just grind down the sharp corners to avoid chipping the gelcoat, says Group. Larger boats might require a hammer with more heft to sound through a thicker outer laminate. “I carry hammers of different sizes and weights for commercial boats and larger yachts with thicker skins,” he says.

And there’s another key characteristic to take note of during tap testing. “When you bring the hammer down and hit a solid laminate, your hand will bounce back to you,” says Perette. “But if you hit a wet area, the hammer does not bounce back as strongly.”

Group agrees. “It’s all about gauging the reflective energy,” says Group. “If the laminate is soft, then energy from the hammer strike will be absorbed into the soft material, just like wave energy being absorbed into a sandy beach.”

Hammer-tapping takes a little practice, says Perette. “You don’t want to beat on the hull,” he says. “All it takes is an easy, smooth rhythm. You almost want to let the hammer do the work.”

Before you grab a hammer and start whacking, carefully inspect the hull. Look for cracks in high-load areas, such as the corners of the transom and around the outboard brackets or engine well, says Group. “Check for cracks on the lifting strakes and cracks just above or below the chines. That is where the bottom and hull side flex in relation to one another. These are all areas of stress in the hull, and if they are moving or are compromised, they are going to show signs of stress.”

Group points out that water generally doesn’t penetrate a laminate through gelcoat cracks alone. “The penetration has to pass through the gelcoat and fiberglass to the core,” he says. “The cracks are often symptoms of a larger issue — that a [structural component] may be compromised.”

Some cracks, indeed, are deep enough to allow water penetration, says Perette. “If you see darkly highlighted dirty cracks, you may have a situation where water is getting to — and mixing with — the core and creating almost a dirty fluid that is being spit out,” he says.

Perette and Group say that water generally enters the core through loose, ill-fitting or improperly bedded deck hardware, seat and rod holder bases, stanchions, hinges and locker latches. “If there are open drill holes scattered about the deck, you know there’s a good chance the core is soaked,” says Perette.

Another simple test is to walk on all surfaces to gauge the solidity of the laminate. “How does it feel?” says Group. “Does the deck have a nice, solid feel, or is it spongy, like a mattress?”

Perette points out that buyers can consult the Web to conduct on-site research when looking at a boat in a marina or driveway. “Use your iPad or tablet to look up the brand and year of the boat,” he says. “There are definitely boats that are known for having problems with wet cores.”

You’ll want to hire a surveyor or lamination expert to fully inspect the hull with more sophisticated tools, such as a moisture meter, but you can certainly conduct the initial inspection. It’ll help you whittle down your list of potential boats that are worth further investigation. Now go find your hammer.

November 2014 issue