Self-Bailing Boats: The Complete Scoop

Check out models offered by the top ten boat manufacturers and you’ll discover that they all build self-bailing boats. In fact, the term ‘self-bailing’ is often seen in promotional material, brochures, and websites as a selling point. But, what exactly does that mean?

What Is A Self-Bailing Boat?

In a nutshell, self-bailing is exactly what it sounds like: a self-bailing boat has the ability to remove water that gets into it without any physical or mechanical assistance. Whenever you see a boat with scuppers at deck-level and above the waterline, you know that it was designed to drain water off the deck or through a gutter system and out through those scuppers. The fact that it was designed to do so, however, is not a guarantee that it actually does.

Many boats, particularly smaller models, only bail when the weight distribution is proper and/or they’re moving forward. On an 18-foot center console saltwater fishing boat, for example, a person sitting in a forward console seat can shift enough weight forward that any water entering the boat will flow towards the bow rather than aft through the scuppers. However, this is also where forward motion comes into play. If that very same boat is moving fast enough to create bow rise, at some point the bow-up attitude would cause the water to flow aft again. In fact, you’ll see some boats which have scuppers that are plugged because they sit below the static waterline. These scuppers would let water flow in when the boat is at rest, but the plugs can be pulled out when the boat’s running to allow water to drain. This is not, of course, what most people would consider to be a truly self-bailing boat.

Another thing you may see on boats with marginal bailing ability are flapper valve or ping pong-ball scuppers (which have a plastic ball held in a casing outside of the scupper, that floats up to block off the scupper when water tries to back-flow into the boat). These are designed to allow water to flow out of the boat when possible, while also blocking the water from entering through the scuppers. However, both are prone to failure, particularly in marine environments where algae, barnacles, and other tiny marine critters may grow and interfere with their performance. In many cases, even leaves, dirt, and similar detritus than gets stuck in the flapper valve or housing can greatly reduce or eliminate their effectiveness.

How Does Self-Bailing Work?

When you eliminate all the variables, self-bailing boats depend on one thing to shed water- gravity. As long as the deck’s height is above the height of the water that the boat is floating on, any water that collects on that deck will attempt to flow downward. The exact height of the deck is a critical feature, as scuppers located near the waterline on a boat with a low deck may allow water to back-flow in when someone walks to the transom and shifts their weight aft, or even when a boat rolls in the sea. However, the higher a boat’s deck is, the higher its center of gravity will be. And on small boats (usually those under 17 or 18 feet long) it may be impossible to have the deck high enough to bail without making the hull sides abnormally tall and the center of gravity so high that it effects other characteristics (such as stability). For this reason, boat designers strive to find a good balance between bailing characteristics, center of gravity, and gunwale height.

As we earlier mentioned, forward motion of the boat can help it in its endeavor to shed water. In many cases boats will also be designed to sit at rest with a slight bow-up attitude, or have an aft-angled deck, to encourage water to run aft and out the scuppers. They may also be slightly crowned for the same reason.

There are, of course, always other variables that do come into play. A big one has to do with whether the deck of the boat is sealed or not. On boats with sealed decks the water has nowhere to go other than out through the scuppers. But any perforation in that deck introduces the possibility that some amount of water will leak into a bilge, fishbox, or stowage compartment. That’s one of the reasons why even boats that bail are still equipped with bilge pumps. Most boatbuilders also combat this reality by adding gutters around deck hatches to drain water to the scuppers, a manifold system, or dedicated overboard drains.

Regardless of whether the deck is sealed or not, another issue can arise due to different design elements that are incorporated into it. In many cases, for example, elevated seat bases are molded into the deck. This has a number of advantages including creating additional stowage spaces, enhancing the stability and security of seats, and in some cases even creating belowdecks areas that may be used to enlarge a cabin. However, the raised surface areas can also interrupt the natural flow of water across the deck. In cases of poor design, they may even cause water to collect and pool in corners or depressions.

Another variable that can affect how well a boat self-bails — or whether it bails at all — is weight distribution. And of course, this variable can change. A well-designed boat that bails perfectly at rest can be set off-balance by bringing gear aboard the boat, adding heavy accessories, or in marginal cases, merely filling a livewell with water or adding ice and drinks to an integrated cooler. A successful day of fishing can even have a downside, if the weight of all the fish you bring aboard causes the scuppers to back-flow or the angle of the boat to shift bow-down.

How Important Is Self-Bailing?

Many boaters would consider self-bailing characteristics to be a critical feature in a boat. Modern bilge pumps work great and are more reliable than those made in the past, but there’s still always the chance of pump failure or a power interruption. So knowing that your boat can naturally shed rainwater and spray without depending on any mechanical devices provides a lot of peace of mind. The exceptions usually arise when builders try to put a self-bailing deck on a boat that’s too small for it to be effective. In this case, they may let just as much water into the boat as they drain out — and in the worst-case scenario, even more.

Even when a boat is well-designed and it bails effectively, having a self-bailing deck is not a silver bullet. Snow, leaves, or detritus can clog the scuppers and reduce or eliminate the boat’s ability to bail. Weight changes may change the boat’s bailing abilities without the captain noticing. And over time, scuppers or hatch drains can become loose and leaky and add water to the bilge. The list of possibilities is just about endless, so even if your boat is self-bailing you still need to have a properly installed and maintained bilge pump belowdecks. Doing so is the best way to make sure that your self-bailing boat always stays afloat.

Written by: Lenny Rudow

With over two decades of experience in marine journalism, Lenny Rudow has contributed to publications including YachtWorld, boats.com, Boating Magazine, Marlin Magazine, Boating World, Saltwater Sportsman, Texas Fish & Game, and many others. Lenny is a graduate of the Westlawn School of Yacht Design, and he has won numerous BWI and OWAA writing awards.

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