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Q&A – Q: Why does my bottom foul before other boats in my marina?

Have a question? E-mail it to or send it to Soundings Editorial, 10 Bokum Road, Essex, CT06426

Q: Why does my bottom foul before other boats in my marina?

A: Many things could cause this. Obviously, the bottom paint you’re using is one possibility. A good, well-established brand may cost more than some others but it’s worth it. And even within brands there often are different paint formulations for different waters and different usages. For example, the waters in the Northeast are very different from the Great Lakes or those of South Florida, and large companies formulate their products to fight the problems of different aquatic environments.

Major companies, such as Interlux, also offer formulas designed for the way you use your boat. For example, there are paints for the boat that sits most of the time and/or runs very slowly, such as a sailboat. Other paints are designed for the boat that goes fast, such as a sportfisherman or center console. You may do better with an ablative paint if you have a sportfishing boat, or an epoxy-based paint if you have a sailboat, depending on the circumstances. Get brochures, call customer service or go to the Web sites of the major paint manufacturers to see what they offer for your type of water and usage.

Other things contribute to fouling. If you’re in an area of heavy nutrients and/or organic life you may have more growth. And some areas of a marina may expose boats to more fouling than other areas in the same marina. For example, some boats may be out where the current flows and brings more nutrients and/or “creatures” into contact with the hull. Or the opposite situation may result in greater fouling; there may be more nutrients and creatures in an area of a marina that is enclosed and has little or no water circulation. The nutrients in this area could come from various sources, such as bird droppings or fish cleaning or even fish. The amount of fecal discharge from fish has always amazed me. You have to be there to see it, and I have because I dive a lot. If you’re not into diving, just for kicks watch what happens in a heavily populated goldfish bowl.

Docks near street runoffs or storm drains could have more nutrients because of animal, human, fertilizer and other organic waste. (Conversely these may have more contaminants, such as oil from cars, which would impede growth, depending upon the circumstances.) Docks near shoreside bulkheads could have increased nutrients in the water because of septic tanks ashore or leaking sewage lines — a problem that’s often more widespread than many realize. In places like this, boats pumping out are actually pumping into the water because of leaks in the municipal pipes up the line.

The water in some areas of a marina might be warmer because of exposure to the sun. Some areas may allow sunlight on the hulls through the water more so than others. It isn’t unusual for one side of a boat to foul more quickly than the other side because it is more exposed to sunlight. And fouling often will be more predominant up near the waterline than down near the keel because the surface layer of water is warmer and exposed to more light. For that reason, and because paint often wears more near the waterline, I put extra coats of anti-fouling around the waterline area.

If you use your boat often, it probably will have less fouling. Moving through the water has a tendency to wash off material that’s in the process of attaching to the hull. If you can get it off before the weed or slime or barnacle attaches, you’re a step ahead. Sometimes fouling begins when currents or even slowly moving but heavily silted waters deposit what is essentially silt on the hull. It’s usually easy to see, just below the waterline. Then creatures start growing in the silt and attaching more permanently to the hull. If you run your boat every weekend this silt deposit will wash off.

If you cruise and take your boat to areas with different types of water, you will find that this can have a tendency to impede fouling. We’ve seen with our boat that some types of fouling may begin to occur in the waters of the Bahamas. However, as we take it into the fresher waters of the Indian River in Florida or other areas of the Intracoastal Waterway or to Chesapeake Bay or New England, the waters of each area seem to kill off some of the fouling that was endemic to previous areas.

Have a question? E-mail it to or send it to Soundings Editorial, 10 Bokum Road, Essex, CT06426