Boat Sealing: Does It Work?

Sealing the inside of a boat is a common practice to prevent leaks. The process involves identifying the source of the leak, cleaning the area, choosing the right sealant, applying the sealant generously, and allowing it to cure overnight. Some recommended sealants include Gluvit, 5200 by 3M, Amazing GOOP Marine, Life-Calk, and Silicone Rubber Sealant. It is important to follow the directions on the sealant package to ensure proper curing and waterproofing.

Sealing methods for different hull materials

Sealing methods for hulls depend on the materials used in the construction of the boat. For example, if the hull is made of aluminium, sealants such as 5200 by 3M, Gluvit, or Amazing GOOP Marine are recommended. These sealants are designed to fill leaking rivets, punctures, or breached seams.

For wooden boats, a traditional method involves caulking or corking the seams with cotton yarn, followed by a paste-like material called paying compound. When the boat gets wet, the wood and cotton swell, compressing the seams and preventing water ingress.

For model boats, the sealing method depends on the material. For example, if the hull is made of High Impact Polystyrene Sheet (HIPS), a polyester resin should not be used as it will melt the plastic. Instead, a two-part epoxy coating or a water-based coating, such as Deluxe Materials Eze Kote, can be used.

In general, sealing a boat involves creating a continuous line without gaps, using materials that can deflect and fill voids to ensure a watertight seal.

Sealants for aluminium boats

Sealing the inside of a boat is important to prevent leaks and protect against leaks in the future. When it comes to aluminium boats, there are several sealants that can be used to get the job done effectively.

One of the most commonly recommended sealants for aluminium boats is 5200 by 3M. This sealant has been widely used in the industry and is known for its good reputation. However, some users have reported that it becomes brittle after curing and cracks when the aluminium flexes. It also has a pasty consistency, which makes it difficult to spread and manipulate into a smooth finish. Additionally, it needs to be used all at once, as it turns into an unusable brick within 1-2 days.

Another popular sealant option for aluminium boats is "Amazing GOOP Marine" or simply "GOOP". GOOP has proven to be tougher and more elastic than 5200. It has superior adhesion strength to aluminium and is less expensive. It also has the perfect viscosity for penetrating and sealing leaky rivets and seams. Additionally, it is reusable and cures fast.

When choosing a sealant for an aluminium boat, it is important to consider factors such as adhesion strength, flexibility, ease of application, and cost. GOOP ticks all these boxes and is therefore a recommended option for sealing aluminium boats effectively.

To further enhance the protection of your boat, it is advisable to overcoat your rivets and seals with a high-quality boat coating. This adds an extra layer of defence against leaks and ensures the long-term success of your sealant. One such coating is the "Wetlander" boat coating, which has excellent adhesion to both aluminium and the sealant itself. By combining the use of GOOP and a boat coating like Wetlander, you can create a robust and complete leak-stopping system for your aluminium boat.

Boat preparation before sealing

Sealing the inside of a boat is a crucial step in boat maintenance, especially if you want to protect your boat from water damage. Here are some detailed, direct, and instructive steps on how to prepare your boat before sealing to ensure an effective and long-lasting seal:

Assess the Condition of Your Boat:

Start by evaluating the current state of your boat. Identify any damages, cracks, leaks, or worn-out areas that require attention. Check for signs of rot, mould, or loose, missing, or broken nails and screws. Pay close attention to the condition of the wood, steel, aluminium, or fibreglass, as this will impact your sealing approach.

Clean and Prepare the Surface:

Ensure the surface is clean and free of any debris, old sealants, or previously applied products. Sweep or blow off loose debris, and then pressure wash the deck with a low-pressure setting (no more than 12,000 psi). Apply a suitable deck cleaner and scrub with a stiff-bristled brush. If you're looking for a natural alternative, you can try baking soda and vinegar, oxalic acid, or a citrus-based cleaner.

Sand the Surface:

Use sandpaper to sand the surface and create a better adhesion for the sealant. For wood decks, opt for medium-grit sandpaper, while for fibreglass decks, use fine-grit sandpaper. If possible, consider sandblasting the steel, aluminium, or fibreglass for optimal results.

Prime the Surface:

Apply a coat of primer to seal the surface and prevent the sealant from soaking into the material. For aluminium boats, you can use a product like PermaFlex or a marine sealant. Allow the primer to dry completely, which may take several hours or even overnight. Ensure the surface is dry before proceeding to the next step.

Choose the Right Sealant:

Select a sealant that suits your boat's material and the climate you live in. For aluminium boats, "Amazing GOOP Marine" is a recommended option due to its toughness, elasticity, and strong adhesion. Other options include polysulfide sealants, polyurethane sealants, and epoxy sealants, each with their unique properties and applications.

Gather the Necessary Tools and Materials:

Before you begin sealing, ensure you have all the required tools and materials, including brushes, rollers, sandpaper, cleaning agents, and, of course, your chosen sealant. Having everything on hand will ensure a smooth and efficient sealing process.

By following these steps, you'll be well on your way to effectively sealing your boat and protecting it from the elements. Remember to always refer to the manufacturer's instructions and take the necessary safety precautions when working with sealants and coatings.

Choosing the right sealant

There are four main types of marine sealants:

• Silicone Sealant: One of the most common sealants, it is highly versatile and easy to use, but has the weakest adhesive properties. It is highly resistant to heat and chemical damage and can be used on wood, metal, and plastics.
• Polyurethane Sealant: Another common sealant that has the strongest adhesive properties. It is easily damaged by chemicals but can be used on wood, metal, and some plastics.
• Polysulfide Sealant: A rubbery and versatile sealant that is easy to work with, though not as pliable as silicone. It has average adhesive strength and is highly resistant to chemical damage. Polysulfide is compatible with wood and metal but not plastics.
• Polyether Sealant: This sealant combines good adhesive qualities with great resistance to water and chemicals. It forms a strong adhesive bond and is highly resistant to heat and chemical damage. Polyether can be used on wood, metal, and some plastics.

When choosing the right sealant, it is important to consider the trade-off between adhesive strength and sealing ability. Silicone sealants provide weak adhesion but make great gaskets and seals, while polyurethane sealants have strong adhesion but don't create very effective seals.

For jobs that require a very strong adhesive bond, such as repairing deck and hull joints, polyurethane sealants are the best option. However, for fittings that need to be repaired or replaced, a permanent adhesive like polyurethane can make removal difficult and damaging. In such cases, a polyether sealant or a lower-strength polyurethane may be a better choice.

The ideal sealant should remain flexible and elastic once cured to form a watertight or airtight seal. Soft, rubbery sealants that can compress to fill gaps between surfaces are ideal, while rigid sealants are less effective. Sealants that retain their elasticity after curing can better handle movement and create a stronger bond.

For sealing teak decks, polysulfide or polyether sealants are recommended as they can flex and move with the expansion and contraction of wooden boards in changing weather conditions. Silicone sealants are a good choice for sealing through-hull fittings as they create effective seals, and the bolts can be tightened to provide adhesion.

The curing time of sealants varies, with some taking several days and others curing in a few hours. Polysulfide and polyurethane sealants cure faster in wet conditions, so atmospheric conditions should be considered when choosing. If you plan to use the boat soon after repairs, select a sealant with a curing time of less than five days.

When choosing a sealant, it is important to consider compatibility with the material being sealed. Always consult the manufacturer's directions, as some sealants are harmful to certain plastics.

Application and curing techniques

The first step in sealing your aluminium boat is to identify the source of the leak. Dry out the boat and monitor for leaks, paying close attention to seams and rivets, as these are common sources of leaks. Once you've identified the leak, it's important to prepare the area by cleaning it with an aluminium boat cleaner to ensure a smooth and clean surface.

When it comes to choosing a sealant, opt for one that is specifically designed to adhere to metal, such as Life-Calk or Silicone Rubber Sealant. These products will protect your metal and prevent corrosion. Apply the sealant generously, as it's better to have excess sealant than not enough. You can always scrape off the excess later.

After applying the sealant, follow the directions on the product to ensure proper curing. This usually involves keeping the boat stable and undisturbed overnight. Once cured, inspect the seal and test its waterproofness.

If you're unable to flip your boat, consider using a sealant like Gluvit, which can be applied from the inside of the hull. Alternatively, you can try a two-part epoxy paint that can be rolled on from underneath the boat. For a more permanent solution, some people suggest using a hoist or jack system to safely raise the boat and access the underside for sealing and painting.

To enhance the seal and provide long-term protection, consider using a flexible boat coating, such as Wetlander, over your rivets and seals. This will create a robust, waterproof system and protect the integrity of the seal.

Frequently asked questions