Five Things You Should Know Before You Buy a Used Boat

1. Fuel Tanks

Most powerboat fuel tanks are made of steel or aluminum. Steel can rust and aluminum can corrode. Steel tanks can last a long time unless they are exposed to water. Exposure to water sometimes happens from leaks in the deck fills above the tanks, or from water sprayed off of the shafts at the stuffing boxes. The tanks gradually rust until the pitting becomes so severe that leaks develop. Most of the tank will appear to be in great shape, and the deterioration might be hidden in a difficult to access area.

Aluminum tanks can corrode from the inside out. Water collects (from condensation) and sinks to the bottom of the tank where bacteria grows. This mixture can lead to corrosion of the tank on the inside.

Aluminum is the most common choice for replacement tanks. Regardless of the material, fuel tank replacement can be costly. At best the process involves cutting the tanks apart in place and replacing them with multiple smaller tanks so that they will fit through the opening. Replacement as single tanks often requires moving the engines, increasing the cost substantially. Fuel tank replacement on a typical 42’ powerboat will cost tens of thousands of dollars, perhaps as much as $50,000 if the engines have to be removed.

For these reasons fuel tank inspection is a critical part of the process. Access is usually very limited. A bore scope can be helpful to look around corners and into tight spaces.

Cutting apart the steel tanks so that they can be removed in small pieces. Old tank removed.
New aluminum tanks ready for installation. New tanks in place. Note inspection ports and sight tubes.

2. Hard Chines and Hard Sleeping

Many cruising powerboats have hard chines. At anchor, these boats have a tendency to produce a “slapping” sound, as motion of the water converges on the pocket created by the chine. If the master stateroom is forward, the result can be surprisingly disturbing. Some people find that the noise disrupts their sleep to such a degree that they sell the boat. Not all hard chines are the same (see photos), and some are worse than others.

The step in this hard chine will generate a “slap” against the hull at anchor. This hard chine has a much softer edge and will generate less sound than the boat in the left photo.

3. Teak Decks

Teak decks add beauty and a wonderful natural non-slip surface. There are two areas of concern: the condition of the wood plugs that cover the screws, and the condition of the black seam compound. If the screws are exposed, moisture can work its way down into the deck structure, eventually causing major damage. Stains in the headliner might be telltale indicators that moisture is getting into the sub-deck, as shown in the photo below. The screws must be removed, the holes bored slightly deeper, and the fasteners screwed in. A new teak plug is then glued in place and trimmed. The seam compound gradually loses its adhesion and elasticity, allowing water to get under the teak, where it finds its way to the screw holes. Re-caulking the deck requires many man hours of labor to reef out the old seam compound, clean the seams, and prep them for new seam compound. The new compounds retain their elasticity longer than the older formulations. If you are having this work done make sure the yard uses a “bond breaker” per the caulking manufacturer’s recommendations. These problems can be easily identified, and the cost to restore the integrity of the teak decking can be quantified before making a purchase offer.

Plugs have worn through, exposing screw heads. Caulking pulling away from edges of seams.
Stains on the forward cabin headliner were caused by water getting into the sub-deck through the deck screws and caulking. We caught this before there was too much damage to the plywood core. Seams have been cleaned and sanded, and new caulking is being applied.

4. Dark Hull Colors

Dark colors have gained increasing popularity for their striking appearance. Hulls generally come from the builder with a gel coat finish. Dark blue gel coats look spectacular for a few years, and then dull and chalky until painted. Once painted with a product like AwlGrip® the dark color will look good for years. If you are looking at a used boat with dark gel coat, keep in mind that a paint job will likely be in your near future. Additionally, dark hulls are much hotter than light colored hulls. In southern climates this difference can affect cabin temperature and air conditioning needs.

This dark blue gel coat lost its luster and the only way to restore it will be with a paint job. The blue still looks good on this boat. The photos below show the temperature on the open transom door compared the hull.
On an autumn day the white transom door shows a temperature of 82 degrees. The dark blue reads almost thirty degrees higher.

5. Moisture Meters on Deck

Bottom blisters have been widely known about for many years, and virtually all surveyors and most buyers are well prepared for this concern. Moisture in the deck and cabin structure however, is equally, if not, more important. It is critical that the survey process include the use of a moisture meter on the deck and cabin. It is also important to know what kind of core has been used in the deck and cabin. The presence of excessive moisture in a balsa core has more serious implications than in a closed cell foam core structure.

Hardware penetrations through a cored deck can lead to moisture penetration. A moisture meter would have pointed to this deteriorated balsa core material.

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