Generally, you shouldn’t see water inside the boat’s bilge that often. However, if you often see water in the bilge, something in the boat needs to be fixed. We will now see the main reasons why you will get water in the bilge.
Water gets collected in the bilge either due to loose screws, damaged bellows (on sterndrives), loose hose connections, loose rub rail, livewells, leaks on the hull, faulty seacock/thru-hull, loose drain holes/plugs, leak in a cooling system, bad seals on the prop shaft, loose speedometer pickup hose.
Those are the most common places to look after if you see water in the bilge quite often. Even if you have an automatic bilge pump, you should not be expected to take care of a problem like this. So, even if you see small quantities of water inside the bilge area or engine compartment or elsewhere on the boat, try to address it quickly.
First, here’s a small table showing the likely cause of the leak, depending on the boat’s state, so that sometimes, you can narrow it down quickly rather than checking all those 14 reasons one by one.
| When You Will See Water In The Bilge? | Likely Cause (But Not Always) |
| While the boat sitting, Idle? | It could be a loose hose, drains, thru-hulls, damaged steering pin seals, or any seal (gasket) on the boat. |
| While the boat is running (underway)? | It could be a loose Rub Rail (Hull Cap Separation), loose speedometer pickup hose, or cooling system. |
If the boat sits idle and turned off in the waters, a loose rub rail or cooling system will not take any water, but any loose thru-hulls, hoses, bad seals like bellows on sterndrive can take water easily.
So, those are just likely causes how a boat can take water, but sometimes they may be wrong. That being said, we will now see those in a detailed way.
1. Loose Screws
- You might not have anticipated it, but even the loose screws on the boat hull (if any) can take some water. Screws that are three to five turns lose can take more significant quantities of water if the vessel is left idle in the water for a long period.
- Sometimes, just tightening the screws on the hull is not an adequate repair. You have to ensure that the water is not coming out of that screw. Even screwing holes for depth-finder transducers on the boat also can take on water if those screws aren’t tight enough.
Tip – 1 If you see water in the bilge only while running, then it is more likely (but not always) to deal with a rub rail seal between the deck and the hull.
2. Damaged Bellows (On Stern Drives)
- If you have a sterndrive, the smart move would be to start inspecting the issue from the engine. Many stern drives have flexible gaskets, called “bellows,” that seal the water out where the universal joint, shift cable, and exhaust run between the boat and drive.
- Their flexibility allows the drive to trim and turn while underway, but they can dry out and crack due to heat, harsh weather, or age. You can visually tell whether the bellow is in good condition or not. If you see any visible cracks on the bellow, replace it.
- Even if you see any slime (algae) around it, it implies some water that is already present inside the vessel is leaking through it. But, of course, if you keep the boat outside dry, then only you can see the slime because if the bellows are damaged, water will come through the damaged bellow and can become wet.
3. Loose Hose Connections
- Hoses are another important thing to check if you see water in the bilge area. Thoroughly inspect all hoses and fittings first. Plastic hoses or couplers, or fittings all can degrade or crack or loosen over time and are very common.
- Again a physical inspection is sufficient if they are located outside or close without further ripping of the boat. Even speedometer pickup hose coming loose from the back of the speedometer will take the water. But, it only leaks when the boat is moving fast. So, check all the hoses.
Related Post – Can A Boat Sink From Rain? Check this article to know the main reasons for how a boat can sink from rain and some essential prevention measurements to take while keeping the boat in the water during rains.
4. Loose Rub Rail (Hull Cap Separation)
- Suppose you see the water getting into your bilge only while underway; a loose rub rail could be the overall culprit. A rub rail hides the joint between a boat’s deck and hull. Since if you see water coming into the boat only while underway, it is a common place water gets forced into.
- Boatbuilders glue the deck to the hull, and often the adhesive there fails. If the glue loses its property, gaps will form between the deck and the hull. Water can easily enter through those gaps, especially while moving in the waters where water gets forced into.
Check this small and very helpful video by Danger Marine on finding a leak on the boat hull, narrowing down the problem.
5. Livewells On A Fishing Boat
- If you are using a fishing boat and often use Livewells on the boat, then it could be the culprit. At the top of the Livewell where it meets the deck is sometimes not sealed well, and water can run over the top and down into the bilge. Look inside Livewell at that seam.
- Also, a full Livewell while coming up on the plane will overflow into the bilge if not sealed at the top. And even if the Livewell is cracked or the drain plug is not there, some drain into the bilge. So, ensure the protection around the Livewells as well.
Related Post – Are Fishing Boats Worth The Investment? Check this article to know whether buying fishing boats are good or bad, along with their pros and cons in a detailed way.
6. Leaks On The Hull
- If the hull is damaged or has a hole inside the hull, the water flows into the boat, and sometimes even the bilge pump may not be sufficient enough to pump it out at the incoming phase.
- Inspect the hull entirely from the keel to the deck properly, and don’t miss out on any minute details. If you keep the boat in the water all the time, then you need to take it out of the water for inspection and put it on a trailer for better visualization.
Tip – 2 If you see water in the bilge while sitting idle, it is more likely (but not always) to deal with loose connections. It can be a loose hose, drain, seals, etc.
7. Faulty Seacock On Thru-hull Holes
- Thru hulls on the boat’s hull are small holes on the hull and can be used to expel wastewater, such as from a sink, to let seawater in, such as for engine cooling, or to allow placement of sensors such as depth finders. If the thru-hull is loose or cracked, it can send water in.
- Even if the seacock value around the thru-hull is not functioning, it won’t close the opening properly, thereby sending the water in. If the thru-hull is below or just above the waterline and it is damaged, all the water outside can easily get inside the boat, sinking the boat.
- Remove the boat out of the water and visually inspect the thru-hull holes. Check for any loose or broken or visually messed up thru-hulls that would be causing a leak.
8. Loose Drain Holes
- Drain holes on the boat are used to drain the water that comes into the boat. Boats with drains require a plug (known as a drain plug) for closing the drain. The drain helps boat owners to get as much water out of the boat after being out on an ocean or lake.
- The plug needs to be installed before the boat goes out on the waters to prevent more water from getting inside. If you keep them open while running on the waters, it can take more water if they are especially close to the waterline. So, often closing them is good.
- Remove the boat out of the water and visually inspect the drain hole. Check for any loose or broken, or visually messed up drains that would be causing a leak.
9. Leak In Cooling System
- Boat engines need water to cool down the engine by flowing inside it over the power and cylinder heads, absorbing the heat. Without the water, the engine overheats because the impeller melts down without water flowing through, resulting in not pumping the water inside the engine.
- Suppose there are any leaks inside the water-flowing tubes; it can sometimes result in water inside the boat bilge. So, you need to check all those connections as well. To check whether there is a problem with the tubes, connect the water hose to the engine and start the engine.
- Open the engine and inspect the leaks on the lines. If you see any water coming out of any lines, you found the issue and change those tubes. Otherwise, no need.
Related Post – Do Boat Engines Need water? Check this article to know more about how the boat engine cooling system works and why boat engines need water in a detailed way.
10. Bad Seals On Prop Shaft
- Have you ever wondered how you allow a 2-inch-diameter propeller shaft to penetrate through the bottom of your hull, give it enough freedom to spin up to 6,000 times a minute, yet not allow water to pass through the hole? The “seals” on the prop shaft will prevent the water from entering inside the boat through the prop shaft.
- These Prop shaft seals are similar to gaskets and made out of rubber. So, they can dry out and crack due to heat, harsh weather, or age. You can visually tell whether the seal is in good condition or not. If you see any visible cracks on the seal, replace it.
Tip – 3 If you are testing your boat to find out leaks, thoroughly close all the thru-hulls and drains and then take the boat out in the water to narrow down the leaks, finding the cause quickly.
11. Loose Speedometer Pickup Hose
- A speedometer on a boat works by using a pitometer. The pitometer works by comparing how fast your boat is going against the speed of the water you’re traveling on. This works by measuring the speed of water coming into a tube compared to air pressure to give an estimated speed figure.
- Speedometer pickup hose coming loose from the back of the speedometer will take the water. But, it only leaks when the boat is moving fast. So, you need to check the speedometer pickup hose as well.
Others
- Faulty Exhaust System. Ever since water has been used to cool exhaust gases, there are many cases of engines flooding with water from the exhaust system (source).
- Waves hitting the boat and Rains.
- Damaged steering pin seals on both sides can let in a tiny amount of water. Usually, the Pins are made of steel and can rust, creating pitting and wearing the bushes, which in turn creates a leak. Interestingly this leak is extremely common on all outdrive boats.
Check this video on Finding a leak on the boat.
Final Tip – To find out the leak on the boat, take the boat out of the water (keep it on the trailer) and fill the bilge with water to find out the leak. But if the leaks are too high on the boat, this method may not work.
The Key Takeaways From The Post
Here are the main reasons why you will get water in the bilge.
- Loose Screws. Even screws that are three to five turns lose can take more significant quantities of water if the vessel is left idle in the water for a long period.
- Damaged Bellows (On Stern Drives). If you have a sterndrive, the smart move would be to start inspecting the issue from the engine. Since it is a gasket (made out of rubber), it can damage as it ages.
- Loose Hose Connections. Hoses are another important thing to check if you are often getting water in the bilge. Thoroughly inspect all hoses and fittings first.
- Loose Rub Rail (Hull Cap Separation). Suppose you see water coming into the boat only while underway; a loose rub rail could be the overall culprit.
- Livewells On A Fishing Boat. At the top of the Livewell where it meets the deck is sometimes not sealed well, and water can run over the top and down into the bilge.
- Leaks On The Hull. If the hull is damaged or has a hole inside the hull, the water flows into the boat.
- Faulty Seacock On The Thru-hull. If the thru-hull is loose or cracked, it can send water in.
- Loose Drain Holes / Plugs. Check for any loose or broken or visually messed up drains that would be causing a leak.
- Leak In Cooling System. Since boat engines need water to cool down the engine by flowing inside it over the power and cylinder heads, absorbing the heat. Suppose there are any leaks inside the water-flowing tubes; it can sometimes result in water inside the boat.
- Bad Seals On Prop Shaft. These Prop shaft seals are similar to gaskets and made out of rubber. So, they can dry out and crack due to heat, harsh weather, or age. You can visually tell whether the seal is in good condition or not.
- Loose Speedometer Pickup Hose. Speedometer pickup hose coming loose from the back of the speedometer will take the water.