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How to Clean a Boat Hull and Bilge Effectively

Properly maintaining your boat helps you to keep its value high and ensure top performance, and one key aspect of boat maintenance is cleaning the hull, inside and out. Keeping the hull clean will help your boat last longer and always look great. Below is our step-by-step guide on how to clean a boat hull. 



man cleaning a boat


How to Clean the Exterior of a Boat Hull

Exterior boat hull cleaning is a relatively straightforward process using fresh water with other cleaning products as needed. 


Step 1: Remove your boat from the water

Ideally, the first thing you will do is pull your boat out of the water to perform a well-rounded inspection. By removing your boat beforehand, you'll also be doing your part to protect the environment as the cleaning chemicals you use during this process can hurt the organisms in the water. While there are many areas you can go to clean your boat, some marinas offer designated areas that may prove useful. (If your boat is large and/or a boat ramp or hoist is unavailable, see “How do you clean a boat hull in the water” below.)


Step 2: Clean all debris

This is likely the most important step of the cleaning process. Over time, scum, debris, and stains invariably build up on the hull's surface. If you notice any large pieces of debris stuck to the hull, remove them before getting started on the more comprehensive cleaning process. Any other substances on your hull can be washed away with cleaners and solvents. 


Step 3: Use fresh water while rinsing

Once you've removed all of the dirt and debris, you should be ready to rinse your boat off. This step should always be done with fresh water to remove any remaining solvents or chemicals before you return your boat to the water. 


Step 4: Completely dry the hull

Next, you need to dry the hull, which can typically be done only if the boat is cleaned on land. The hull must be dry before you attempt to apply any wax. 


Step 5: Apply a protective wax

The final step in the cleaning process involves waxing the hull, which gives your boat a much better appearance. Waxing is not necessary if the topsides of your boat have been painted within the last few years; this is common on larger and older boats. The value of waxing, particularly on the fiberglass gel coat of most boats, is that it limits UV damage and helps protect your boat until the next cleaning. Make sure you wait 10 to 15 minutes for the wax to dry once it's been applied. 


cleaning a motorboat


How to Clean a Boat Hull Interior

Clean the interior areas of your boat's hull with brushes, towels, and environmentally friendly cleaning products to get the best results. 


Step 1: Properly scrub the interior bilge

The bilge is the lowermost portion of the boat's interior where everything naturally collects. Along with bad odors, it's common for mold, rust, and engine oil to accumulate in this area. Use a combination of fresh water and bilge cleaner to scrub the bilge clean. 


Step 2: Use seat cleaner on boat seats

Boat seats often become stained as a result of UV damage. You can restore the appearance of your seats by vacuuming up any trapped dirt, scrubbing the materials with a seat cleaner, and drying off the seats with a towel. If any stains remain after you apply the seat cleaner, the towel should remove the rest. 


Step 3: Clean your boat deck with a specialized cleaner

Nothing's more harmful to the appearance of your boat's interior than a dirty deck. From dirt and oil to grease and stains, substances can build up in the non-skid patter found on most boat decks. Before putting your boat back out on the water, remove these with a mixture of fresh water and deck cleaner. Always use a soft-bristle brush when scrubbing the deck. 


boat hull cleaner


General Tips on Cleaning Your Boat

There are some basic tips to keep in mind when cleaning your boat, which include:


• Choose cleaning solutions based on the materials you're cleaning

• Select a biodegradable and environmentally friendly soap that comes with a neutral pH

• Use soft cloths that effectively absorb liquid solutions

• During the cleaning process, remove dirty water with a wet/dry vac



The following answers some of the most commonly asked questions on the best way to clean a boat hull.


How do you clean a fiberglass boat hull?

There are numerous cleaning solutions that can be applied to a fiberglass boat hull. Even though it's highly effective, avoid using muriatic acid unless you hire a professional. While muriatic acid is the main solution used when cleaning fiberglass boat hulls, it's a caustic acid that can damage your boat as well as your health. If this acid gets on your skin or eyes, the damage may be irreversible. 

Many of the stains on your hull can be removed with basic soap and water. However, any mineral or organic stains require a more potent solution. Use cleaning products that are specifically designed to remove mildew and rust. Keep in mind that harsh chemicals can damage your boat's gel-coat surface.


How do you clean an aluminum boat hull?

If you have an aluminum boat hull, use warm water and mild detergent. When you use abrasive cleaners, it's possible that you'll damage the finish.


How do you clean the bilge?

To clean the bilge in an eco-friendly manner, use a biodegradable bilge cleaner. This cleaner should be poured into the bilge tosoak for at least one hour. Once it's done soaking, it should be easier to remove stains and dirt buildup. Make sure you use fresh water when rinsing out the bilge area, and capture any bilge waste for proper disposal at a waste management facility.


How do you clean boat hull stains?

Most stains on your boat hull can be removed with a combination of warm water and a hull stain cleaner. Rinse the area with pressurized water to remove deeper stains.


How do you clean a boat hull in the water?

You can clean your boat hull even when it remains in water by using a scrubbing pad, sponge, and snorkel or scuba tanks below the waterline. In salt water, make sure you complete this process frequently to avoid heavy growth including barnacles on your hull. To clean the topsides above the waterline, use a small dinghy that you can tie close to the hull.


How do you clean a boat hull on a trailer?

If your boat is on a trailer to clean, most areas of the hull should be easy to access. Use the cleaning tips mentioned above to remove most stains. For difficult-to-reach areas, consider placing a brush attachment on a water hose. Waxing can also provide protection for these spots.


How often should you clean a boat hull?

Depending on usage and if it stays clean where you store it, boaters typically clean the exterior of their boat hull every one to three months and clean the interior after each use.


boat cleaning and maintenance


Boat Cleaning Products

Some of the products you can use while cleaning the hull of your boat include:


• Towels and microfiber cloth

• Sponge

• Bucket

• Alcohol wipes

• Vacuum

• Bilge cleaner

• Seat cleaner

• Stain remover

• Soft bristle brush

• All-purpose cleaner

• White vinegar

• Dish soap

• Baking soda

• Spray bottle


boat deck cleaning


Sustainable cleaning products

When you're searching for sustainable cleaning products that won't damage the environment, even if they get into the water, make sure you identify the solution's toxicity and biodegradability. You can also make homemade boat cleaners that take the guesswork out of the equation. 

While cleaning your boat may be a time-consuming process, it pays dividends by allowing you to maintain performance and avoid costly damage. With this guide in hand, you should have everything you need to get started to clean the hull.  


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Written By: Toi Williams

Toi grew up in coastal New England, Her parents had a second home on Newfound Lake, in New Hampshire. Because of this, Toi was able to enjoy boating at sea as well as in the Lakes Region of New Hampshire. Today, she regularly wakeboards and waterskis on her Malibu wake surfing boat. She also sailed at sea in Maine, and taken many trips to the Isles of Shoals.

More from: Toi Williams

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