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When It Rains, Boats Sink


A heavy rainstorm has the potential to sink boats, but it doesn’t have to be that way.

Keeping rain from sinking a boat requires proper design as well as owner involvement.

Let me start with a few apparently false assumptions. The boats we use should be designed to float even when it rains. Bilge pump systems should be able to expel water from boats to keep them afloat when there is a hose failure or … even when it rains. Finally, designers and builders should design and build boats to handle the weather and to not sink … even when it rains. Now, we all like to think that when we are out plying the waters of our rivers, bays, and oceans that our boats are well equipped to keep us afloat and safe, right? But what about when she (yes, I still call boats “she”) is left alone to fend for herself dockside? According to a study done by BoatUS, the majority of boats (69 percent) sink dockside or while the vessel is moored. Such was the case on August 13, 2014, when torrential rain with five to eight inches of the stuff hit several areas on the Jersey Coast in just a couple of hours. In the wake of the storm, dozens of boats were at the bottom or hanging from their lines dockside … But why?

I was tasked to clean up the carnage. While handling the salvage operations and ensuing loss evaluations, I focused on both the damage and the “why” the boats sank. While not too surprising to me (I had 30+ years of handling damage claims under my belt), taking the time to document the findings in a detailed way left me wondering, “What could prevent these sinkings?”

In every case, the cockpit scuppers were overwhelmed, and/or the deck drains, hatch covers, gutters, and engine compartment lips failed to keep the water from draining into the bilge. The flooding became progressive in nature. This is nothing more than a practical application of Bernoulli’s principle of fluid dynamics. With more water in the bilge, the boat sat lower on her lines, and then even more water, at an ever-increasing volume, down-flooded or back-flooded into the boat and bilge through the scupper or freeing ports in the hull. The result is a salvage job and often a constructive total loss.

The well scuppers of this boat were directly at the waterline. A hatch mounted in the well allowed water to leak into the bilge, eventually sinking the boat.

Example #1: 25-foot Sportfisher

The scuppers were below the waterline at the transom and just at the waterline in the cockpit. Directly forward of the port and starboard side scuppers were hatches that led to the bilge. The hatches were not dogged down, and the manufacturer had made no attempt to seal them. Water failed to drain out of the scupper system fast enough, and the boat began to take on water through the leaking hatches into the bilge, overwhelming the bilge pump. As the boat became heavier, the scuppers submerged under water, and that was that.

Lack of gaskets on hatches can allow a leak from a deluge to fill the bilge.

Example #2: 24-foot Center Console

Fitted directly ahead of the outboard in the engine well was a hatch for access to the bilge, pumps, and wiring. The hatch was originally fitted with a gasket, but the gasket was worn, and the hatch was not dogged down. The well scuppers allowed a constant flow of water into the outboard well, which drained into the bilge. Over time, the pump failed and the boat sank.

Example #3: 16-foot Flats Boat

The vessel was repowered with a heavier four-stroke outboard that replaced the original two-stroke. The boat was floating, but right on the edge of disaster. Along came the rain, and down she went.

Example #4: 25-foot Older Walk-Around Cuddy

The boat had originally been designed as an inboard/outboard (I/O) model but was built, straight out of the factory, with an outboard on a bracket. The manufacturer replaced what should have been the sealed I/O engine cover with a regular deck hatch. The scuppers were just at the waterline. The hatch was not sealed or dogged down, so rainwater accumulated quickly and flooded the boat until she sank.

Failed Bilge Pumps Don’t Sink Boats

I could go on and on because these sorts of scenarios repeated themselves again and again. That said, there were several consistencies throughout this event. Time and time I would hear that either the boat sank because the bilge pump failed or simply that the rainwater could not drain out of the boat fast enough, or it was draining into the bilge — or a combination of the two.

Let me make one thing perfectly clear: Boats do not sink because bilge pumps fail. They sink because we fail to keep the water on the outside of the boat. So let’s not blame this on the bilge pumps. Bilge pumps are designed to remove nuisance water and minor leaks. They provide a short-term solution, not long-term maintenance relief. So why do boats sink when it rains? Let’s look at some very common problems first, and then get into how boat owners can stop worrying when it begins raining.

The most common problem is simply hatching openings in decks that are not bogged down and are not fitted with proper gaskets to make them watertight. Many of these hatches (mostly plastic) are fitted right in front of the outboard well to facilitate access to the outboard mounting bolts, pumps, and hoses. Water backs up in the scuppers and drains directly into the bilge. The pump works and works, but eventually, the battery to which it is connected becomes discharged, and down she goes.

These float-ball style scuppers often are installed when water backflows into the boat. They’re not designed to keep a boat afloat.

Next is simply poor design in scupper or freeing port location. The American Boat & Yacht Council (ABYC) has recommended standards for the placement of scuppers, scupper sizes, and the minimum heights above the load waterline of scuppers both while the boat is static and at maximum heel. Time and time again, we see scuppers that are right at the waterline and often well below the waterline due to poor design, though sometimes this happens when boat owners put too much stuff in the stern. An immediate sign of a pending problem is a boat with float-ball-style scuppers to prevent back-flooding; if you’re considering such a boat to buy, don’t walk away from it — run. Cockpit decks are supposed to be designed to be a minimum of four inches above the waterline but aren’t always. Even when a slight amount of water drains into the bilge, the result is disaster because the boats may be designed on the edge with little safety margin. Throw in an anchor and some chain back there, and there’s no margin when that big rainstorm hits.

Repowering is a problem, too. Comparisons between two-stroke and four-stroke outboards show a weight difference of 10 to 20 percent — which could easily be a couple hundred pounds in a dual-engine installation. This weight is at the transom, the location of most scuppers, or even further aft if the engine is on a bracket. This changes the load waterline, and openings that were once perhaps well above the waterline are now just at or below the waterline, putting the boat at further risk of sinking.

Corrugated hose is a poor choice for scupper drains. Use polyester reinforced tubing instead.
This cockpit drain leads not overboard, but right to the bilge, relying on the bilge pump to keep the boat afloat in the rain.

Another pet peeve: Why do designers and builders of boats seem to put hoses and thru-hulls in the most inconvenient (and inaccessible) places? If you can’t inspect your hoses and fittings, you may not know your drains are leaking or your hoses are cracked until the sky unloads on your boat. Our fleet of recreational boats is aging. Hoses that were designed to last perhaps 10 years are now 15 or 20 years old. They are brittle, cracked and failing, yet we cannot see them, let alone service them. I have had occasions where the decks have had to be cut or inspection plates installed just to get to the junction of the thru-hull nipple, hose, and clamp.

This boat had been recently repowered with a heavier four-stroke engine that brought the scuppers down too low for the boat to survive a deluge.
The cover on this boat filled with rainwater, and because the scuppers were already at the waterline, they back-flooded, and the boat sank.

Another favorite is the deck that appears to be self-bailing; I mean it has beautiful scuppers, nice hatches, is well above the load waterline, only to find out that the deck drains lead to hoses that drain into the bilge and not overboard. Disaster awaits. I fully understand that in the good old days, boats did not have self-bailing cockpits. Take for instance an old Herreshoff 12-1/2 or your normal skiff where if the boat was not covered, it filled up with rainwater. But today, if a boat is designed with a fiberglass liner and a deck that completely covers the bilge and it has drains that look like they would drain overboard, it is just plain lazy and a poor design, in my humble opinion, to have them drain into the bilge. Sure, the bilge pump may keep her afloat for a time, but she will sink and it may not be dockside the next time it may be 100 miles offshore.

Bad design: This scupper drain hose is completely inaccessible for servicing.
A hose is only as good as its clamps. Cheap clamps look like this after a short time; use quality all stainless-steel hose clamps.

Lastly, let’s take a look at normal and expected maintenance. Here are a few things that come up over and over. Outdrive universal joint and shift boot bellows: they should be inspected every year and replaced every third year, give or take. The rubber dries out and begins to crack and leak, which may be the difference between weathering the storm or not. The gimbal bearing and gimbal housing may leak water into the bilge. Plastic corrugated hoses: In my opinion, there is no place on a boat for these, unless well above the waterline. They are thin-walled and become brittle, crack, and fail. Livewell plumbing: I have seen livewells that drain into the bilge. These are often well below the water, and many have no seacock to shut off the flow of water into the well. The well fills up and, worst case, drains into the bilge or adds weight, bringing the load waterline down enough to cause flooding through the scupper. Again, think of these things as contributing to the reason so many boats sink due to rain. It might be the straw that broke the bilge pump’s back.

For most of the sinkings in Jersey that week, poor hatches were to blame. They were either badly built, poorly located, or unsealed — often collecting lots of clogging dirt. OK, let’s assume that I buy the need for the scuppers to be near the waterline. To be clear, I don’t buy it. Still, shouldn’t the hatches in the decks and all deck openings be impervious to leaking? Would you go down in a submarine with shoddy fiberglass hatches and no seal? Oh, we need them to look nice, you say? Well, my answer to that is that a nice aluminum hatch with a positive-locking system and gaskets that are waterproof look just ducky. If your deck hatches and inspection ports don’t have gaskets, install them. Make sure they can be dogged down, and do that when you leave the boat so that the next big rainstorm can be shrugged off.

In the end, I’ll say it again: A simple heavy rain should not sink a boat while floating dockside in calm water. If your boat is not equipped to handle rain at the dock, how safe are you at sea?

Daniel Rutherford

Contributor, BoatUS Magazine