The Leak Eternal

(or A Case of the Soggy Bottom Blues)
by Sherwood Heggen

The general public believes an old wooden boat is supposed to leak. That belief is seemingly accepted by many owners of wooden boats. They live with the water in the bilge and protect their boat from sinking with maybe a second bilge pump. Having observed and experienced leaking boats lately, it seems timely at the end of this boating season, to discuss leaky boats. If you should be among those who own a “Leaky Teaky”, now is the time to determine the course of action for a drier boat next season.

In general, most every boat will take on some water, but shouldn’t require a bilge pump to work overtime to keep up with the inflow. It would be worth our time to think about the really leaky boat for a bit. What has come to be accepted as “that leaky old boat” is more likely signs of trouble brewing or conditions that are potentially dangerous. Let’s get a mental picture of what could be if some due diligence isn’t exercised to ward off any chance of disaster.

The picture is a beautiful Saturday morning in June. You go to the dock to set off on a short trip around the lake. To your horror, your beautiful treasure is hanging by its mooring lines. It was afloat yesterday when you went for a ride! What happened?! In this case, any number of things could have happened. Understand that what was afloat yesterday, is not guaranteed to be afloat today. You can, however, be proactive in addressing the problems or conditions that might jeopardize your boat.
Initially, we are going to review the mechanical items that could allow water into the boat.

Your hull may be perfectly sound but water could flood into your boat and sink it in minutes if you have a siphon tube with a plugged vent hole. The siphon is designed to draw water from the bilge while underway. While sitting tied to the dock, the boat may take a big wake or be caused to move violently which can cause a rush of water up the siphon tube from the lake. With the tube filled with water and the vent hole plugged, water can begin to siphon in the reverse direction into the boat. You may not even know you have a siphon on your boat, so go look for it. If there is one, you will find it in front of the gas tank of a typical runabout or utility. It is the shape of an inverted “U”. At the top you will find a small hole. Be sure that hole is clear of any debris. It would be a smart idea to remove and clean the siphon tube to be sure there is nothing in the tube that will ultimately plug the supposedly cleared vent hole. Or, remove it altogether and plug the hole in the bottom permanently. Rely on the bilge pump to keep the incoming water in control.

Unfortunately, similar circumstances can exist with the bilge pump. Installing a through hull fitting for the pump hose too close to the waterline can create a sunken boat. Any time water has a chance to enter, it will. Lets say the pump quits working for whatever reason. Even though the boat is tight, it could rain really hard and weigh down the boat with rain water. This could lower the boat in the water dangerously close to the through hull fitting. Water could then flow directly to the pump if the hose goes directly down to the pump. If the hose rises considerably above the water line in the shape of an inverted “U”, the problem lessens. Yet, that appears to be the same as the siphon tube and the hose doesn’t have a vent hole to protect from siphoning. It should be mentioned here that a reliable battery is a must if you intend to leave your boat unattended for any period of time in the water and away from a lift.

Let’s consider the shaft log and rudder log as a source of leaking. Most boaters understand that the common shaft log is going to drip water a tiny bit. That is necessary for lubrication of the packing. When there is a dribble or flow of water coming from the shaft or rudder log, there is trouble. The packing nut may have come loose or the packing might be worn out. Inspect other through hull fittings, such as, the intake strainer for seawater to the engine, the drain plug, or any other through hull fitting on the bottom that could allow the water to enter and sink your boat. The rudder log does not need to allow water to pass freely for lubrication as does the prop shaft which spins at a high rate of speed.

The exhaust pipe hole in the transom planks is often an overlooked source of leaks. Packing can work loose, wood can rot, etc. Exhaust pipes have been known to contain water in them when the weather turns cold. The water freezes, expands and cracks open the pipe. Then, when the weather warms up and the boat goes into the water, a lot of cooling water from the engine is dumped into the bilge when the engine is running. Water also enters the exhaust pipe from wave action and drains into the bilge. Other sources of water: leaky water pumps, loose seawater hose to the engine, missing drain plug in the block, loose or missing frost plug, etc.

The above can all be fixed relatively easy. But, what if water is constantly coming, unrelated to the above items, even though the boat has had time to soak for a reasonable time? If there isn’t a recognizable reduction in the period of time between bilge pump operations after the boat has been in the water for a day, there is more than likely a problem that swelling the bottom is not going to resolve. If the bottom and frames seem sound, but water continues to enter, search for the source of the leaks. Where do you start looking? How do you find the leak?

If the boat is out of the water and on a bunk trailer, fill the bilge gradually with a garden hose. Be sure your hull is totally supported by a good bunk trailer if you do this. Water is very heavy and will be applying downward pressure rather than inward pressure. You could damage the hull if done improperly. Be watchful for where the water starts to leak through as the water rises in the bilge. Common trouble spots are the forward garboard plank/keel seam, chine to topside chine plank rabbet, transom to
bottom boards, or any where there is a seam or joint. If that method isn’t practical, the boat can be floated to locate the leaky area. But, to be able to see the entry spot of the water, the floors must be removed. Once the boat is floating, be quick to notice where the water is entering before a lot of water in the bilge disguise its entry point. Take note of that point, but do not consider that to be the only point. Keep looking. Often the bilge is wet seemingly all over. The tools required here to identify where the water is coming from are a flashlight to peer into the dark recesses of the bilge and a big sponge or two. Dry out an area to see where the water is running from. If you can see that the water is flowing from the back, for instance, determine if it is new water or residual water from around that area. Absorb water with the sponge farther back to see if water continues to run into the dried area from the back. You may follow residual water all the way back to the transom. Finally, you might see new water coming in at the transom base, or farther out at the transom corners. While down there you might get lucky and find loose change, small toys that children drop into the clam shell vent hole, or the boat’s registration card you thought you had lost. Regardless, you will find something, and hopefully, it is the source of the leak.

Now, what is causing the leak? Is it broken screws or bolts; rotten or cracked boards? Is there a rotten seam batten not holding the screws anymore, as would be the case of a Century bottom. Almost without fail, an original Century transom base will be delaminated, leaving the bottom screws no place to hold. Chris Craft, Century and other planked bottoms may have spread over time, leaving gaps in the bottom seams which may have been filled with caulking by some well-meaning owner. Then starts the cycle of swelling against the caulking and spreading even further, requiring more caulking.

How does one fix or seal the leaks? It depends on the problem certainly and has to be considered a case at a time. Then, use your boat building skills to correct the problem accordingly.

If the bottom of the boat is original and it has been used regularly for the past 40+ years, there may be no easy fix. If you can scratch off chunks of wood from the bottom frames with your finger nails, your boat bottom is no longer sound. If the planks are cupped or any shape other than flat to the bottom frames, there is a big sign of trouble. If there are a lot of plugs missing on the bottom, it is likely screws are loose because of split or rotten frames. If you find those conditions are causing leakage, give yourself some peace of mind and replace the bottom. The process is 30+ years overdue.
Keep in mind that the bottom is the most critical part of the boat. You can run the boat with a tattered deck, beat up topsides, and a lawn chair for a place to sit. But if the bottom is questionable, it is only a matter of time before it goes down. Don’t destroy it, restore it.

If you have a question regarding leaky bottoms or other concerns about restoring your boat, feel free to call me at 715-294-2415, or e-mail me at