Sealing An Aluminum Boat: Tips For Success

Owning a boat can be a lot of fun, but it also comes with maintenance. If you have an aluminum boat, you may eventually need to seal it to prevent leaks. Aluminum boats are constructed with seams and rivets, which can be prone to leaking if they get loose. To seal your aluminum boat, you'll need to identify the source of the leak, clean and dry the area, and then apply a suitable sealant. It is important to choose a sealant that is specifically designed to adhere to metal, such as Life-Calk or Silicone Rubber Sealant. When applying the sealant, it is better to be generous as you can always scrape off the excess. After sealing, you should follow the directions for a proper cure and then test the seal for waterproofness.

Sealant types: Marine GOOP, 5200, and Silicone Rubber Sealant

When it comes to sealing an aluminium boat, there are several types of sealant that can be used. Here is a detailed overview of three popular options: Marine GOOP, 3M 5200, and Silicone Rubber Sealant.

Marine GOOP

Marine GOOP is a highly versatile, tough, and strong adhesive, that is part of the GOOP range of products. It is specially formulated to be UV resistant, making it perfect for outdoor applications on boats. It can effectively bond to a variety of materials, including vinyl, rubber, metal, glass, and wood. Marine GOOP is also temperature resistant, abrasion resistant, and waterproof. It can withstand temperatures ranging from -40 °F to 180 °F (-40 °C to 82 °C) intermittently. In terms of application, the surface should be clean, dry, and free from dirt. For optimal results, the surface can be roughened before use. It is recommended to allow the sealant to cure for 24 hours, although full cure times can range from 48 to 72 hours depending on the environment.

3M 5200

3M 5200 Marine Adhesive Sealant is a powerful and versatile sealant, ideal for bonding marine substrates like wood, fibreglass, and metal. It is designed to be tough yet flexible, making it suitable for various applications such as deck housings, hull fittings, and porthole mounting. One of its key advantages is its ability to resist saltwater and weathering both above and below the waterline. The sealant provides a long working time, taking up to 4 days to fully cure. It is important to note that this sealant is intended for industrial and occupational use only and is not for consumer sale or use.

Silicone Rubber Sealant

Silicone rubber sealant, such as the 3M Marine Grade Silicone Sealant, is a high-quality option for above-the-waterline interior and exterior sealing. It is designed to resist mildew and yellowing, and can adhere to a variety of surfaces including bare and painted metal, fibreglass, glass, non-oily woods, and plastics. This type of sealant is typically flexible and can withstand harsh marine environments. It is also non-sagging, making it easy to apply even on vertical surfaces. It becomes tack-free within 20 minutes and fully cures in 24 to 48 hours.

Sealant qualities: Toughness, elasticity, adhesion, price, and shelf life

When selecting a sealant for an aluminium boat, there are several qualities to consider to ensure the best performance and longevity of the seal.

Toughness and elasticity are important factors, especially for aluminium boats that navigate shallow waters. The sealant needs to be able to withstand abrasion, jarring and flexing of the aluminium surface. A sealant that is too brittle will crack when the aluminium flexes, compromising the seal. A good way to test the toughness of a sealant is to stretch it and see at what point it breaks. Additionally, performing a tear test will indicate how well the sealant holds up when cut. "Amazing GOOP Marine" sealant, for example, has proven to be tougher and more elastic than other brands, making it a good choice for aluminium boats.

Adhesion is critical to the long-term success of the seal. Seals can lose adhesion with flexion or impacts, so a sealant with strong adhesion to the aluminium surface is essential. Understanding the substrate and sealant properties is vital to ensuring optimal adhesion. In some cases, chemical bonds can be formed, increasing the strength of the bond. For instance, chemical bonds are formed between silicone and glass, polyurethane and glass, and epoxy resin and aluminium. "Amazing GOOP Marine" sealant has been shown to have better overall adhesion to bare aluminium than other brands, making it a top performer in this category.

Price is also a consideration when choosing a sealant. "Amazing GOOP Marine" sealant, for example, is half the price of a similar-sized tube of 5200 Marine Fast Cure sealant, making it a more economical choice.

Finally, shelf life is an important factor, especially if you are not using the entire product at once. "Amazing GOOP Marine" sealant, for example, has been reported to have indefinite shelf stability after initial use, whereas 5200 Marine Fast Cure sealant needs to be used all at once, as it turns into an unusable brick within 1-2 days.

By considering these sealant qualities, you can make an informed decision when choosing the best product for sealing your aluminium boat.

Sealant application: Be generous with the sealant and always read the label

When it comes to applying sealant to your aluminium boat, it's important to be generous. It's better to over-seal than under-seal, as you can always go back and scrape off any excess sealant. However, if you under-seal, you may have to start all over again, and this could mean removing the old sealant. Some products will adhere to themselves, but it's always best to check the label to understand the specific product you're working with. Taking a few seconds to read the label could save you hours of manual labour.

So, how much sealant is enough? Well, this will depend on the size of your boat and the number of leaks you need to seal. As a general rule, it's good to have more sealant than you think you need. That way, you can ensure that you have enough to be generous with the application and don't run out halfway through.

When applying the sealant, follow the directions on the label. Most boat sealants will need to be left to cure overnight. After this, you should inspect the seal and test to see if it's waterproof. It's also a good idea to protect the sealant from UV damage with paint or carpet.

There are a variety of sealants on the market that are suitable for aluminium boats. Some popular options include "5200 Marine Fast Cure" and "Amazing GOOP Marine", which have been praised for their toughness, elasticity, and strong adhesion to aluminium. Other options include "Life-Calk", "Silicone Rubber Sealant", "JB Weld", and "Gluvit". When choosing a sealant, opt for one that is specifically designed to adhere to metal and will not corrode aluminium.

Leak identification: Find the source of the leak, dry the boat, and inspect for more leaks

Leak identification is a crucial step in sealing an aluminum boat. Here are some detailed instructions to guide you through the process:

Firstly, find the source of the leak. This can be a challenging task, as boat leaks can be difficult to locate. Begin by thoroughly inspecting your boat, paying close attention to areas where leaks commonly occur, such as hull fittings, seacocks, valves, hoses, instrument senders, and running gear. Check for any signs of wetness or dripping water. Use your fingertips to feel for moisture, as they can often detect leaks that are difficult to see.

If you have a leak below the waterline, dry the boat and keep an eye on the bilge to identify the direction from which the first trickle of water arrives. This will help narrow down the possible entry points. Remember that leaks can be deceptive, and water may travel through hidden conduits and inaccessible compartments before appearing in the bilge.

If you suspect a leak in an inaccessible area, consider adding an inspection port to better reach and examine those spaces. In some cases, you may need to cut an access hole to pump out water from enclosed compartments.

If you have an aluminum boat, pay special attention to seams and rivets, as these are common sources of leaks. Dry the boat completely and carefully watch for any signs of leakage in these areas.

Once you have identified the source of the leak, it's important to dry the boat thoroughly before proceeding to the next step. Use paper towels or dedicated aluminum boat cleaners to ensure the area is completely dry. This will provide you with a smooth, clean surface to work on.

Finally, before sealing the leak, inspect the boat once more for any additional leaks that may have gone unnoticed during the initial inspection. This step is crucial, as it ensures that you address all leaks and prevents the need for further repairs in the future.

Leak prevention: Over-coat rivets, seams, and seals with a high-quality boat coating

To prevent leaks in an aluminium boat, it is important to over-coat rivets, seams, and seals with a high-quality boat coating. This process helps to stop leaks and protect against future leaks. While using a sealant is a good start, it is not always enough to ensure a robust and complete leak-stopping system.

There are a variety of sealants available on the market, each with its own advantages and disadvantages. For instance, some sealants become too brittle after curing and crack when the aluminium flexes, while others have weak adhesion to the aluminium. It is crucial to select a sealant that is both tough and elastic to withstand the stress of abrasion, jarring, and flexing.

Once you have chosen an appropriate sealant, such as "Marine GOOP", it is essential to apply a high-quality boat coating over the seals. This coating serves as a protective layer that safeguards the integrity of the seal and defends against future breaches. Many boat paints do not adhere well to sealants, so choosing the right coating is vital. Look for a flexible coating with excellent adhesion to both the sealant and the surrounding aluminium.

One example of a suitable coating is "Wetlander", which can be applied over the rivets, seals, and the floor or hull of the boat. This creates a double-protected waterproof seal, ensuring that your boat remains leak-free. Not only does this coating help to seal the rivets, but it also reduces their exposure, making them less likely to catch on something and tear open. Additionally, an anti-friction coating like Wetlander can help the boat slide over surfaces more easily.

By combining a high-quality sealant with an effective boat coating, you can be confident in your boat's ability to withstand leaks and keep you safely afloat.

Frequently asked questions