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On Powerboats

The value of self-bailing cockpits

“Water management” is certainly a prosaic way of putting it. It could means all sorts of things depending on whether you work for the Tennessee Valley Authority, tend bar or maybe moonlight as a lock operator on the Erie Canal. But if you hang around boats long enough, there are really two ways of thinking about the subject: whether deck water ends up in the bilge or back over the side.

Other than in hard-core inboard fishing boats, it’s increasingly common to see poorly thought-through cockpit scupper systems. Cockpits don’t drain completely because drains are higher than decks, hoses (susceptible to coming loose, with lamentable results) are needed to bridge the void between the cockpit liner and hull side, and scuppers and hoses often are far too small to provide an adequate drainage rate for anything more than light rain or washdown water, even in supposedly offshore-capable outboard fishing boats.

The boatbuilder’s standards-setting organization in the United States — the American Boat and Yacht Council — doesn’t differentiate between bowriders meant for lake use and 35-foot center consoles that routinely fish 80 miles offshore when it comes to cockpit drainage capacity. In Europe, boats are divided into four seaworthiness categories, and this makes a lot of sense for the U.S. market as well, since boatbuilders would be held to a higher and more definitive standard, and consumers would have a clearer idea about a boat’s actual (not marketed) capabilities and limitations.

With self-bailing cockpits, the most basic approach is seen in smaller outboard fishing boats and some of the larger sterndrive runabouts with small scuppers and drain lines that channel incidental hose, bucket or rainwater over the side instead of into the bilge. The idea is to make cleanup easier and keep the bilge clean. The scuppers on these boats are too small and the cockpit decks too low for any positive impact on seaworthiness, but any kind of self-bailing deck sure makes the boat more enjoyable to own. And if you keep it on a mooring, unattended for weeks at a time, since the water’s not draining to the bilge to be pumped over the side by the bilge pump, you won’t have to worry as much about running your battery down.

If I were looking at two otherwise equivalent 25-foot bowriders and one had a self-bailing cockpit and the other didn’t, I know which one I’d pick. That’s one reason I’m a big fan of dual consoles; they have the bowrider’s layout but with their higher decks and self-bailing cockpits they have the center console’s added seaworthiness and ease of maintenance.

The other kind of self-bailing makes the boat more seaworthy by quickly shedding water back over the side. Boats that venture offshore need to be able to get rid of large amounts of water that come aboard, and fast. Whether your boat meets the very basic convenience criteria or the rigorous safety standard ought to depend on its type, size and mission, and intended service. Once you are aware of the ramifications of the minimalist, convenience-driven design vs. the more robust drainage capability of the well-found offshore boat, you just might go boat shopping with a little more insight and choose one boat over another because of its virtues in this area.

Why drainage rate matters

You’re offshore in your open center console, running into short and steep breaking 4- or 5-footers, and you stuff your bow into one of them. You suddenly have a situation on your hands that only foresight on the builder’s part can bail you out of (so to speak). Imagine that in about two seconds you took several hundred gallons on board — a little more than a ton of water. It’s sloshing around the deck of your 25-footer, and you’re suddenly heeling 25 degrees to port. There are two immediate issues (besides forgetting where you put the life jackets).

One is whether the deck is high enough so there’s enough reserve buoyancy to keep the deck above sea level and allow the water to drain. The higher the deck, the more reserve buoyancy. If you’re in, say, a 33-foot Grady-White with the cockpit 14 inches above the waterline at full load, you have tons (literally) of reserve buoyancy to help you out of this predicament. If you’re in the average bowrider or wakeboard boat with the deck at or even below the waterline at full load, you’ve got a real problem. Of course, that’s why the prudent bowrider or flats-boat owner stays in the lake and doesn’t follow that Grady offshore.

The other issue is how fast all that water can drain back overboard, and that’s a function of how big the scuppers and drain lines are, and how many there are. How fast is a big deal not because we’re worried about your topsiders drying out, but because all the water sloshing back and forth on deck creates free-surface effect, which greatly reduces stability. And while the high deck creates lots of reserve buoyancy, it also raises the boat’s center of gravity that much more when it’s covered with water, further reducing stability. While you need the high deck for the reserve buoyancy, you also need the water to drain overboard immediately, if not sooner (as my grandmother used to say).

Let’s back up for a minute and have a look at the guidance boatbuilders have for building boats. The ABYC is the standards-setting organization affiliated with the National Marine Manufacturers Association. Most boatbuilders belong to the NMMA, and NMMA members must comply with ABYC standards to remain members in good standing. (It used to be voluntary, so good for the NMMA for making it a condition of membership, as the result in many cases is a better boat for the consumer).

That said, while it offers excellent guidance in many ways, the ABYC either has little to say about some safety areas or, in some cases, sets the bar a little lower than I am personally comfortable with (boarding ladder length, bow railing height, cabin overhead hatch size, etc). But since it doesn’t set higher seaworthiness standards for 30-foot deep-vee offshore center consoles than it does for 20-foot bowriders, you really need to understand your own boat’s capabilities and limitations.

If your boat was built to the ISO standards used in Europe, it would be assigned a design category based on stability, freeboard and buoyancy — key measures of seaworthiness — and its maximum displacement. The four design categories specify the waters (sheltered, inshore, offshore, ocean) and maximum sea state (wave height) in which different boats can operate. ISO rules also differentiate between the need for either basic self-bailing (rain and washdown water) decks or quick-draining cockpits, which must drain from fully flooded to 4 inches of water on deck in 40 seconds to five minutes, depending on the boat’s design category. A “quick-draining” cockpit also has a minimum height of the deck above the full-load waterline, which determines reserve buoyancy.

The ABYC’s guidance on scuppers is brief. First, it specifies that “scuppers and all components must be at least 1-inch internal diameter.” The problem is that a 1-inch scupper will have a glacial draining rate and will clog easily on anything from pine needles to fish scales. Another problem is that the scupper strainers often clog just as easily, like the strainer in your kitchen sink. These strainers usually are perforated or slotted, and the ABYC says they have to be 50 percent larger than the scupper, which makes sense. But you’re still left with a too-small 1.5-inch strainer that plugs easily.

The ABYC says that the cockpit, filled completely with water to the “fixed sill height,” must drain 75 percent in 90 seconds, with drain lines (a lot bigger than 1 inch) sized accordingly to an ABYC formula that takes into account cockpit volume. But the reality is that a boat will be very vulnerable to capsizing during this agonizingly long minute-and-a-half (remember the free surface effect). I, for one, would be a lot more comfortable with a standard that required 95 percent drainage in 15 seconds for an offshore boat.

Scupper anatomy

It used to be that scuppers were basically large holes cut in the sides of the hull, usually at the transom and at deck level, to let water out quickly. With a hole that’s 8 inches wide and 3 inches high in both corners of the cockpit at the stern, and with the deck pitched aft and cambered from side to side, deck water can find its way overboard in a hurry, even when listing. And nothing smaller than a 10-pound bluefish will plug it up.

On the charter boats of my youth, those big hull-side scuppers also made cleanup quick and easy. If we shipped a little water over the stern when backing hard on a fish, it drained back overboard in no time at all. And since the scuppers were right in the corners of the transom, the water made like a horse for the barn, out and overboard. No puddling and sloshing around hunting for the nearest exit. Those scuppers also were recessed a little below deck level, so there wasn’t anywhere for the last few ounces of water collect and stain the deck.

While the ideal scupper is a simple hole in the side of the boat, the reality with many of today’s boats is that hoses are needed to bridge the gap between the cockpit liner and the hull side. And hoses can work fine as long as they’re big enough — say, 2 to 3 inches in inside diameter — and run downhill and exit well above the waterline. The bigger they are, of course, the faster they’ll drain, and the less likely they are to clog. The height of the deck is important, since in addition to the importance of adequate reserve buoyancy a low deck will be a wet deck, especially when fishing.

Most scuppers work in both directions, letting at least a little water in when backing down or just rolling in the trough — even boats with those little flappers over the scupper openings on the outside of the hull. Of course, it’s easier to handle a fish when you’re close to the water, up to point, but there’s a lot to be said for just buying a longer gaff.

The ABYC also says a scupper hose exiting the hull below the waterline (measured when the boat is fully loaded and heeled 7 degrees to one side) must have a seacock — a sensible rule — and that it should be “readily accessible, capable of being reached quickly and safely under emergency conditions without the use of tools, with handles that are easy to operate.” The problem is, because of their location way back aft and outboard in the bilge on the average outboard fishing boat, these seacocks can be tough to get to. And a seacock that isn’t cycled open and closed regularly likely will be frozen shut when you need it.

A good way to solve the problem is have the hose exit the hull well above the waterline so it doesn’t need a seacock, which in turn calls for a higher deck than many boats have today. But even higher hoses leave the boat vulnerable to sinking if they fail, which is why I prefer old-style above-deck, plumbing-free scupper holes.


The bowrider or flats boat is self bailing so the washdown water goes over the side instead of into the bilge, not so it can shed a boarding wave. This is perfectly reasonable as long as the cockpit deck is high enough to provide adequate reserve buoyancy for inshore use and the scupper design and location make it easy for the water to drain completely. However, the convertible or triple-outboard 35-footer that ventures 80 miles out should meet the quick-draining criteria. If you buy a small runabout, wakeboard or ski boat that doesn’t self-bail, that’s fine. Just be aware of the limitations and be careful about where and in what conditions you operate.

I like some of thesimple-yet-effective design elements of the past that are being rediscovered. Look at cabin windows. Regal has started putting big windows in its Window Express Cruisers so their cabins don’t seem like caves. But this is basically resurrecting an old design (using modern frameless glass technology) that always made good sense, like the 1960s-era trunk-cabin EggHarbors and Pacemakers. Taking the same approach to scupper design, so they drain more quickly and completely, would make for safer, lower-maintenance boating.

So what does all this mean? Make scupper design (size, number, location, recessed or proud of the deck, etc.) part of the decision-making process next time you go shopping for a boat. All else being equal, choose the boat with the big corner-mounted scuppers that drain quickly and completely. Knowing your life will be easier, and your family safer offshore, will make boating all the more enjoyable.

Eric Sorensen was the founding director of the J.D. Power and Associates marine practice and is the author of “Sorensen’s Guide to Powerboats: How to Evaluate Design, Construction and Performance.” A longtime licensed captain, he can be reached, and his book purchased, at .