4 steps to fix a leak on your boat


By Keith Dahlin

Back in the early ’90s, I lived aboard my Columbia 28 while attending university. I often walked down the dock like a kid in a candy store, making note of the boats I liked (and wanted). One in particular always made my mouth water. A few slips down from me floated September, a classic, beautifully lined Cal 40.

While walking to the marina early one morning, I found September 6 feet deep. Only the mast and spreaders placed the boat within its slip. Shocked and bewildered, I later found out that a seacock or hose connection failure had caused the boat to sink. I imagined it silently sinking in the middle of the night.

Years later, I learned that a 1-inch hole below the waterline with water rushing in at 35 gallons per minute would have put September’s decks awash within 45 minutes. Unknown to me at the time, I had been witness to two heartbreakingly common statistics: To quote BoatUS Insurance, “for every one boat that sinks underway, four sink at the dock” and “failed thru-hull fittings account for 50% of all sunken boats at the dock.”

Last summer while checking a seacock for a vanity sink drain on a Beneteau 46, I gently bumped the head intake seacock with the back of my hand. The next instant, bright green bubbling seawater filled the dark, cramped cabinet! Checking the head intake had been on my list; now it immediately shot to the top—along with my heart rate.

[pullquote type=”right”]Checking the head intake had been on my list; now it immediately shot to the top—along with my heart rate.[/pullquote]

As an ASA sailing instructor, I often pull a speed transducer out of its through-hull to demonstrate how to clean the marine growth off the paddle wheel. When the water surges into the boat at 75 gallons per minute or 1.25 gallons per second, there isn’t a calm nerve in the boat. After five long seconds and 6 gallons of seawater, I stop the breach with a tapered wooden plug, drawing a large sigh from my audience.

Back on the sinking Beneteau. With my heart rate as high as a kite and the butterflies in my stomach operating at hyperspeed, I dove across the main salon, opened the forward port storage cabinet, grabbed the emergency supply box and threw off its lid. Inside I found various sizes of wooden plugs and a bright orange, conically shaped foam plug. Although familiar with the new orange Forespar TruPlug, I had never used one.

Each second felt like an eternity. I grabbed the fancy foam plug, rushed back to the eruption and plunged the orange spike into the hole. I’ve seen this type of plug work in demo mode, but the current performance seemed less than perfect. The through-hull broke off with sharp, jagged edges, so I had to knead and pinch the cone into the hole for fear of tearing it by twisting it in. I couldn’t stop the disturbing dribble of seawater, so I replaced the foam plug with a wooden one, which turned the dribble into a less anxious drip.

Lessons learned

  1. Memorize the location of every hole in your boat.
    Make a laminated diagram with the location of each hole labeled with its purpose (intake, drain, prop shaft, etc.), and tape the diagram to the top of your navigation station. If water starts lifting your floorboards, you can quickly check the weakest links first. If you don’t know where to look, you could lose crucial minutes by panicking.
  2. Have emergency equipment on hand to handle every through-hull, seacock or hose failure.
    Through-hulls and seacocks typically range from a half inch to 2 inches in diameter; therefore, different size holes may require different size products to stop the flow of water. Tapered wooden plugs range from 9/16 to 1 3/8 inches, and the Forespar TruPlug fits holes up to 4 inches. I have seen a waxy, putty-type product called Stay Afloat but have never personally used it. I have also heard that you could use a small towel, raw potato or carrot twisted or rammed into a hole in desperate situations. Mark and match your plugs (or potatoes!) with each through-hull and store them in an easily accessible container.
  3. Work your seacocks often; open them, close them and give ’em a little shake. (They should not move.)
    Make sure you have functional, corrosion-free bronze through-hulls and seacocks with two 316 stainless steel hose clamps at each end of your hoses. Marelon (ABYC certified) through-hulls and seacocks have been steadily replacing bronze fittings in recent years. Just last year, I swapped out three of my bronze fittings for Marelon, which is immune to electrolysis and is just as durable as bronze with the proper maintenance. Electrolysis was what turned the Beneteau’s through-hull fitting into pink clay.
  4. Check your boat often for water intrusion.
    As often as you can, check that your bilge pumps and batteries aren’t hiding rainwater intrusion or small leaks from the packing gland. Once the battery dies or the bilge pump fails, rain or seawater accumulates, changing the boat’s stability and adding compression forces around your seacock and hoses if the water freezes. Keep an eye on your battery voltage or add a bilge pump monitor.

On the Beneteau in five minutes (about 150 gallons later), the floorboards would have started to float up, indicating a major problem for anyone aboard. Under such a scenario, five minutes could feel like five hours and a lost boat, but in reality, you should have plenty of time to plug a 1-inch hole. So think small (holes), and don’t be a part of a large statistic.

Lt/C Keith Dahlin, AP, of Boulder Valley Sail & Power Squadron, lives in Boulder during the winter and in Santa Cruz, California, in the summer. He uses his USCG 100 Ton Masters license and marine biology degree to teach students about sailing and sea life on Monterey Bay.

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