5 Best Marine Sealant for Aluminum Boats
5 Best Marine Sealant for Aluminum Boats
5 (100%) 9 vote[s]
3M Adhesive Sealant Fast Cure 4200
Cure Time – 24 Hours
Ideal For Joints, Rub-Rails, Access Plates
Seals Above & Below Waterline
Loctite Fast Cure Adhesive Sealant
Watertight, Flexible Bond
Ideal For Through-Hull Fastening And Deck Fittings
Cure Time – 24 Hours
3M Adhesive Sealant 5200
Handling Strength In 48 Hours
Retaining Strong Bonds During Vibration, Swelling, Shrinking
Cures Completely In 5-7 Days
Red Devil 0785 StormGuard
30 Minute Rain Ready
For Exterior Sealing Of Windows, Doors, Skylights
For Wet Or Dry Surfaces
TotalBoat Aluminum Boat Leak Sealer
Can Be Sanded And Painted
Simple Repairs Of Leaking Boat Rivets And Seams
Above Or Below The Waterline

Choose the Best Marine Sealant for Aluminum Boat

Customer’s Choice: the Best Rated Marine Sealant for Aluminum Boats

135 users answered this survey. Please help us improve this review!

44.44% of users selected 3M Adhesive Sealant Fast Cure 4200, 9.63% selected Loctite Fast Cure Adhesive Sealant, 17.78% selected 3M Adhesive Sealant 5200, 0.74% selected Red Devil 0785 StormGuard and 27.41% selected TotalBoat Aluminum Boat Leak Sealer. Every month we analyze your answers and change our rating.

It is no secret that vessels are subjected to enormous loads during operation and can react with various deformations. Exposure to fresh and saltwater and ultraviolet rays has a considerable impact on the service life of boats. Therefore, marine sealants should be necessarily used in vessels’ construction and repair. Boat sealants are used to protect various areas on small boats and larger ships. They are applied for sealing window openings, deck, and hull seams. Sealants have also proved to be efficient for riveted and bolted joints of the vessel.

Since the scope of work of the sealant on the boat is rather large, the requirements for its quality are also high. Sealants for seawater must create elastic vibration-resistant sealed seams, which in turn have elasticity in order not to undergo various types of shrinkage and temperature deformations. Moreover, such sealants must have high adhesion to almost any material, must be resistant to sea and freshwater, ultraviolet radiation, and be durable in operation.

In this article, we will review the 5 best marine sealants and tell you about the main properties of the boat sealants you can find on the market.

3M Marine Boat Sealant – a great solution for underwater patches

3M Marine Boat SealantThis adhesive sealant can be applied directly on the surface as it does not need to be mixed with other components. It cures the boat within 24 hours, and then it is ready to be launched on the water.

The sealant forms flexible bonds that do not get damaged during vibrations and movements. Strong polyurethane polymer provides long service. You can easily remove this semi-permanent sealant without boat damages once you need to replace it.


  • Easy to apply directly from the tube;
  • Long-lasting;
  • Works perfectly below and above the waterline;
  • 24-hour cure;
  • Removable;


  • It will not work as a pure adhesive.

This multipurpose sealant will work fine on plastic, metal, and other materials. It is convenient to use as you can apply it directly from the tube. If you want it to be more fluid, keep the container under warm water before use. The remains of the sealant can be cleaned with acetone. Strong polymer formula makes the sealant effective for joints, crew or bolt holes, and other hardware attachments. It resists extreme weather conditions and saltwater and is very durable. You will also be able to remove it once you need it.

Fast Cure Marine Sealant – a good remedy for small holes in metal and rubber

Fast Cure Marine SealantThis sealer is recommended for curing aluminum boats, thanks to its waterproof property. It provides a perfect bond of plastic or rubber to aluminum surfaces.

The sealant comes in a convenient cartridge, making it easier to apply it without a caulking gun.


  • Water-resistant;
  • Paintable;
  • 24-hour cure;
  • Provides flexible bond;


  • Not heat resistant;
  • A bit difficult to dispense.

The sealant will help you cure many items in your household. You can use it to make emergency patches on a number of items made from plastic, vinyl, fiberglass. It is perfect for patching little holes on your aluminum boat and small repair of pools. Some users found it difficult to get it dispensed, so you may need a putty knife to help. The product comes in bright white color and can be painted after 24 hours since application. But note that it is advisable not to leave it unused in the tube for a long time as it will dry out.

3M Boat Sealant – a great cure for aluminum boat leaks

3M Boat SealantThis flexible sealant will help you in many emergency situations when you need fast and effective repair. It works well on fiberglass, wood, plastic, aluminum. The sealant provides a super-strong bond and long repair effect.

It is especially appropriate for aluminum boats as it builds an impassable barrier to water in the processed places. Alternatively, you can use it on many other items.


  • Permanent bonding;
  • Water-resistant;
  • Perfect adhesion;
  • Simple to apply;
  • Durable formula;


  • Very difficult to remove.

This sealant is the best solution to repair leaking seams in your boat. It is better to use it in warm weather. In this case, it works like a liquid rubber and penetrates everywhere like paint. To achieve the best results, leave the processed item for 5-7 days to cure. The sealant becomes very hard but flexible enough to resist vibration, shrinking, and shock. The processed areas withstand bad weather conditions and saltwater with no issues. You can use it anywhere on an aluminum boat, including shaped seams and underwater areas.

Red Devil Silicone Sealant – super-fast drying boat repairing agent

Red Devil Silicone SealantThis silicone sealant is designed for watertight and airtight protection. RTV formula stands for room-temperature-vulcanizing properties. It means that sealant dries really fast when exposed to the air.

It is recommended for processing windows and doors, dryer vents and skylights. The super-strong adhesive formula allows you to use the product for various indoor and outdoor purposes, including the repair of aluminum boats.


  • Can be applied for wet and dry surfaces;
  • Lifelong guarantee;
  • Super strong adhesion;
  • Works in 30 minutes after application;
  • Can be easily cleaned with solvents;


  • This sealant is not removable;
  • Non-paintable.

The most attractive property of this sealer is its fast curing time. You will need only 30 minutes to have everything ready. It spreads evenly and dries to the state of dense rubber. You will need a bit of the substance for repair. It will help you to easily fix many things around, including non-porous areas of boats. Note that after a tube is opened, the sealant will harden over time.

Leak Sealer for Aluminum Boats – fast boat leakage treatment

Leak Sealer for Aluminum BoatsThis sealant comes as a cartridge containing two tubes. One is filled with resin, and the other contains hardeners. These both automatically mix together in a correct ratio.

The cartridge will fit well with a standard caulking gun. It is recommended to paint over the cured areas to protect them well from UV light. The repaired area will be ready in 75 minutes.


  • Easy to use;
  • Paintable;
  • No need to mix;
  • Water-resistant;
  • Fast-curing;


  • Temperature-sensitive.

This sealant is ideal for repairing rivet holes and leaking seams in your aluminum boat. You just need to prepare the metal surface properly to achieve ideal adhesion. The manufacturer recommends using sealant at a temperature above 40 degrees. However, some users still recommend applying it in a bit warmer environment. You may need a caulking gun if you need to seal many areas. Other than that, you will be satisfied with the result this sealer brings.

Buyer’s Guide

Sealants can be grouped according to several criteria, the most important of which are the chemical base, purpose, elastic properties. The choice of sealant for certain conditions will depend on the set of these features. Often, people struggle when choosing a sealant since the selection is diverse, and the quality of repair and installation depends on the appropriate choice.

Acrylic sealants

It is a polymer that contains acrylic acid compounds. This type of sealant can be applied both externally and internally. However, you should take into account that it changes consistency for softer under the influence of heat, and gets harder in the cold. It can cause its peeling off the surface.

The acrylic sealant is moisture resistant. But during constant contact with water, it loses its adhesive properties, which may result in delamination.


  • Good adaptive quality;
  • Excellently sticks to such materials as metal, wood, and plastic;
  • Works well in a wide temperature range;
  • The sealant is solvent-free (there are no odors when working with it);
  • It is not afraid of UV rays and water.

Silicone sealants

Thus sealing material contains about 45% of silicone rubber. It acts as a base that hardens at room temperature. It will work well on a variety of surfaces like concrete, plastic, aluminum, galvanized metal, as well as wood, stone, ceramics. Silicone sealant can keep for over 20 years after application.

One-component silicone sealant hardens due to moisture in the air.

Two-component sealants use a catalyst for curing. They are mainly used in the industry.


  • Extremely durable. These sealants work for 15-20 years;
  • Resistant to UV radiation and other aggressive factors;
  • Retains its properties in any temperatures;
  • Sticks well to almost all types of surfaces and does need primers;
  • Very flexible and can repeat any shape without deformation;

Polyurethane sealants

It is a synthetic multipurpose material. Its most winning feature is that it can easily replace rubber and plastic.

These sealants are designed for sealing joints and seams in building structures. However, due to its powerful material properties, it has acquired a wide range of applications. Polyurethane sealant contains caustic components. So you must strictly follow safety measures when working with it. It is advisable to use it only in the open air.


  • High adhesion;
  • High elasticity;
  • Withstand mechanical stress and are resistant to ultraviolet light, moisture;
  • Frost resistance as well as the ability to work at low temperatures;
  • Resistant to corrosive agents;
  • Bonds well to various materials, including aluminum;
  • Paintable;
  • Solvent-free;

Does not emit harmful substances after polymerization, as a result of which it can be used in residential premises;

This sealant cures when exposed to humidity.

Bituminous sealants

It is one of the oldest sealants produced using rubber and bitumen. Such sealants do not require special skills. You will literally need half an hour to seal cracks and seams in the roof, boats, drainage system. Bituminous fillers do not dissolve in water, so you may apply them even in high-moisture environments.

The disadvantage is that you will not be able to paint it due to high elasticity, and you will not be able to use them at sub-zero temperatures. But at the same time, this sealant can be used without special preparation of the surface before the application. The high adhesion properties of bituminous sealants allow skipping this stage.


  • High elasticity;
  • Sticks excellently to most surfaces;
  • Resistance to extreme weather conditions;
  • Protects an item from corrosion;
  • They have a high operating temperature range;
  • Rubber sealant can be painted;
  • The service life of these sealants is about 20 years.

Special tips for better results

  • If you are going to use a new sealant, take time to read the instructions. You need to check its compatibility with different materials, application rules, surface preparation rules, etc.
  • Most of the fillers need special pretreatment of the surface. It must be clean, dry, and free from traces of paint, varnish, old coating. You may need a special solvent to degrease the surface;
  • Use the right dose. Do not skimp on sealant, especially if you want to restore the hull below the waterline;
  • Observe the time required for the sealant to fully cure. Most often, it takes from 24 hours to a week;
  • Recheck if nuts are tight enough when using mechanical fasteners with sealant. It will increase water resistance;
  • When working with sealants, use personal protective equipment and work in a well-ventilated area;
  • If you happen to spill or use too much sealant, have acetone and kerosene at hand to remove these. Always read the manufacturer’s instructions on what solvent is recommended for sealant cleaning and removal.

Useful Video: Jon Boat Transom Fix: 3M Marine 4200 Quick Cure 3of3


There are many ways to protect aluminum boats from aggressive environments and repair in case of some issues. Modern technologies allow boat owners to effectively protect their boats from water, moisture, and rust. And marine sealants will come to your rescue when you still find some leakage or holes. We hope this material will be useful for you to learn more about existing sealants and facilitate your selection process.

Hello! I'm a James Miller, and I'm an expert in materials science. I learned different metal properties in the New Jersey Institute of Technology, and I know everything about all kinds of metal. That's why I want to share my experience with you.

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