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Troubleshooting 101: Water in the Boat


“If water can find a way to get in, it will.” It isn’t a proverb, but it should be. Ask anybody with a boat. Chances are good, they’ll have a story.

Most of the time, water stays outside of a boat’s hull. Most of the time. But when it doesn’t, a boater has to make some fast decisions, the most important of which is, how fast is it coming in? Here is a fact you will never remember if faced with the sudden appearance of water around your ankles while boating: a two-inch hole that is one foot below the waterline results in 78 gallons/minute entering the boat. With every minute the hole isn’t plugged, you are adding around 500 pounds of weight to the boat. That ratio increase as the boat sinks lower in the water.

A big cause of trailer boats taking on water is found-or in this case-not found, at the center of the transom. A missing drain plug that is used to close off the cockpit drain when launching is responsible for 12% of trailer boat sinkings (and this usually occurs at the ramp). Maybe more unfortunate is the fact in each case, the boat didn’t have to take on water at all. Forgetting to put a drain plug in happens to all of us. Having a replacement drain plug nearby doesn’t happen enough. It is suggested every trailer boater have a plug either attached to the wheel of the boat or in a place where it can be quickly inserted in the event it is needed. Even at a boat ramp, water will be looking for a way to get in. If you haven’t unhooked the boat from the trailer, it’s probably best to try and pull everything up the ramp and let the water drain while looking for the missing drain plug (if too much water has gotten into the boat however, the tow capacity of your vehicle may have been exceeded).

After reviewing hundreds of claims a few years ago, BoatUS Insurance concluded 30% of boats sink away from the dock as a result of water coming over the gunwales. This happens when the boat is out in seas for which it wasn’t designed (for example, the freeboard is too low and the boat is being broadsided by the waves). Trailer boats, however, get into trouble when waves come over the transom, usually through the “cutout” where the outboard engine is attached. BoatUS Insurance claims reveal 13 of 15 trailer boats that sank away from the ramp, were hit by waves coming over the stern. “Usually this doesn’t happen with a single wave,” says former BoatUS Technical Director Bob Adriance. ” The first one will put a lot of water in the boat but it’s the second or third wave that will swamp it.” Once this happens, a bilge pump isn’t going to be able to offer much assistance because the waves will continue to roll across the cutout as a result of the boat sitting even lower in the water.

One way to get out of a situation like this is to put the engine in gear and slowly move forward, allowing the water to actually drain through the cockpit. The problem, however, is with this much water in the boat, chances are slim the engine is going to start. Of course the best thing to do is never get into this kind of situation. Turning on the VHF weather channel isn’t going to tell you much when the bad weather is already happening.

If the water has come from one heavy wave while underway or from a day or two of rain while at a dock or on a trailer, the cockpit drain is usually capable of getting it out. The key word here is “usually.” Drains get clogged. If you notice water is remaining in the cockpit, first check the drain cover for obstructions (dirt, paper, hair, even seagull droppings have been known to block water’s exit). If this doesn’t produce results, then debris and the technical term called “gunk” is clogging the hose or pipe. Take a look and see where the obstruction is located. But take a look at one more thing as well: is the drain on the outside of the hull sitting below the waterline? If so, then you’ve got trouble (9% of boats sinking at the dock is the result of fittings that were supposed to have been above the waterline but are pushed below by excess weight (from water) according to statistics from BoatUS Insurance). This means there is already a lot of water in the bilge, although most trailer boats 20 feet or less simply use cockpit drains rather than a bilge to handle excess water.

One good piece of news about trailer boat designs is the fact all boats under 20 feet are required to have built in flotation in the hull. While this won’t be of any help whatsoever in heavy seas or in heavy rain, it does mean your boat isn’t going to go to the bottom.

However, in the event you find yourself in the worse situation of all, make every attempt to make a “Mayday” call to the local coast guard, giving location and the number of people with you. Make sure everyone is wearing a personal flotation device and then make sure everyone stays with the boat.

While trailer boats may not have a bilge pump, there are numerous models that are designed with a bilge to hold excess water (and keep it from covering the cockpit). If your boat has one, here’s something to understand about bilge pumps: they are rated on the basis of gallons per hour that can be pumped. The ability to pump 360 (for example) gallons of water per hour may seem like a pretty powerful pump but keep in mind this is based on the pump and the hose and the water outlet all being at the same level. Most, if not all bilges, are below the waterline which means a pump may have to be powerful enough to move water as high as three-four feet above where it is positioned. This means less than the rated capacity of gallons per hour is pumped. And that means your bilge pump may not be up to the job.

The bilge is also home to gunk and debris that has settled after passing through the cockpit. The screens need to be inspected, preferably before you launch at the ramp. Some bilges are designed so the pump actually sits on a ledge above the deepest area and, as a result, has less of a chance of getting clogged than if it were at the very bottom. If your bilge isn’t built this way, give some thought to carrying a replacement screen (or two).

While most trailer boats don’t have thru-hull fittings, statistics prove underwater fittings are the cause of sinking in half the boats left in a slip. These same fixtures were linked to 18% of the sinkings of boats that were underway. Hoses attached to thru hulls or raw water cooling systems or even outdrive boots can be the cause of a boat taking on water. And when this occurs, the speed at which the problem is discovered-and resolved-is crucial. This is why, on days when the boat is on the trailer or in the water, spending five minutes to find potential places water could enter the hull is time well spent.

BoatUS former Technical Director Bob Adriance says part of this inspection should include taking a look at how these hoses are attached. This should be part of the spring inspection but, more important, each hose should all be double clamped to its fittings (especially the cockpit drains). Test the hose itself and determine if there is any leak occurring (chances are good the cockpit drain hose you have is the original).

Knowing where to look if water gets into your boat is the most important step you can take. Knowing what to do is the next. Thinking ahead, however, before the water even gets in, is the best preventive measure of all.

BoatUS Editors

Contributor, BoatUS Magazine