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How to Clean a Boat: Deck, Hull, Underwater Hull and Cabin
Clean a boat from the top down: first the deck and superstructure, then the hull, and finally the underwater hull once the boat is out of the water. Use a pH-neutral boat shampoo, soft brushes and plenty of fresh water, then protect fibreglass with a coat of boat wax.
When cleaning a boat, remember that teak, antifouling and acrylic windows each need their own approach, so only use a pressure washer where it is safe to do so.
What will you learn in this article?
- Why clean your boat regularly?
- What is your boat made of?
- What do you need to clean a boat?
- In what order should you clean a boat?
- Can you clean a boat with a pressure washer?
- How do you clean the cabin and interior?
- How do you protect your boat after cleaning?
- How often should you clean your boat?
- Which mistakes should you avoid?
- Frequently asked questions about cleaning a boat
- In short: cleaning a boat
Why clean your boat regularly?
Dirt, salt, algae and bird droppings slowly attack the finish. Fibreglass turns dull, stainless steel picks up rust spots and timber goes grey or starts to rot. A clean boat is also easier to inspect: hairline cracks in the gelcoat, loose fittings or worn sealant only show up properly when everything is clean. That way you catch small repairs before they become big ones.
What is your boat made of?
The right approach depends on the material:
| Material | Cleaning | Protection | Avoid |
|---|---|---|---|
| Fibreglass (gelcoat) | Boat shampoo, soft brush | Boat wax or polish | Abrasive cleaners, stiff brushes |
| Wood and teak | Teak cleaner, soft brush across the grain | Teak oil or varnish, depending on the finish | Pressure washer, scrubbing along the grain |
| Steel | Boat shampoo, treat rust spots straight away | Touch up paint or coating | Leaving salt water to sit |
| Aluminium | Mild cleaner | Wax or coating | Acidic or strongly alkaline products |
| Stainless steel fittings | Soft cloth, stainless cleaner | Stainless polish | Steel wool (causes rust) |
What do you need to clean a boat?
- Pump or garden hose with fresh water
- Two buckets: one with soapy water, one to rinse the brush
- pH-neutral boat shampoo, ideally a biodegradable one
- Soft brush on a pole, soft hand brush and sponges
- Microfibre cloths and a chamois
- Boat wax or polish for fibreglass
- Dedicated products for teak, stainless steel and windows
- Gloves and safety glasses when using cleaning products
For flat, sturdy surfaces, a powered brush such as the Batavia Twin Brush can take the effort out of scrubbing. Test it first on an inconspicuous spot to make sure the brushes are not too stiff for your non-slip deck or gelcoat.
In what order should you clean a boat?
Prepare
Take loose items, cushions and lines off the deck. Close windows and hatches. Look for damage while you clear up.
Deck and superstructure
Rinse off loose dirt and salt with fresh water first. Then scrub with soapy water and a soft brush, one section at a time, and rinse each section before the soap dries. Work from the highest parts downwards so dirty water does not run over areas you have already cleaned.
Teak deck
Never use a pressure washer on teak: it strips out the soft wood fibres and leaves the deck rough. Scrub across the grain with a soft brush and teak cleaner, then rinse thoroughly. Let the deck dry before applying oil.
The hull above the waterline
Wash the hull with boat shampoo and a soft brush or sponge. Remove waterline marks and rain streaks with a dedicated hull or waterline cleaner. Rinse and dry with a chamois to prevent limescale marks.
The underwater hull
Only clean the underwater hull when the boat is out of the water. Start as soon as possible after lifting out, while algae and growth still come off easily.
Can you clean a boat with a pressure washer?
On fibreglass above the waterline and on a sound underwater hull, a pressure washer is fine if you keep a good distance and do not aim directly at sealant joints, rubber seals, vents or fittings. Do not use high pressure on teak, on weathered gelcoat with hairline cracks, or on stickers and lettering. If in doubt, a hose and brush is the safer choice.
How do you clean the cabin and interior?
- Cabin: vacuum up dust and sand first. Wipe walls and ceiling with a mild cleaner and a damp cloth.
- Cushions and fabrics: check the label to see if covers can go in the washing machine. Let them dry fully before putting them back.
- Galley and toilet: use products suitable for the systems on board. Harsh drain unblockers and lots of bleach can damage pipes and seals.
- Windows and hatches: many boat windows are acrylic. Use lukewarm water with a little soap or a dedicated plastics cleaner, and never glass cleaner containing alcohol or ammonia.
- Bilge: pump it out, clean with a bilge cleaner and dispose of the water according to the marina's rules.
Prevent mould in the cabin by ventilating, not leaving wet gear on board and standing cushions on end when the boat is not in use. A moisture absorber helps over winter.
How do you protect your boat after cleaning?
UV light gradually makes fibreglass dull and chalky. This is called oxidation. If the gelcoat is lightly dulled, restore the shine with a polishing compound and a polisher on a low speed. Then apply a coat of boat wax for protection. Ideally do this at the start of the season and again halfway through.
Protect wooden parts with teak oil or varnish, depending on their current finish. Keep stainless steel fittings looking good with a stainless polish.
How often should you clean your boat?
- After every trip: rinse the deck and fittings with fresh water, especially after sailing in salt water.
- Monthly during the season: wash the deck and hull, air and clean the cabin.
- Before and after the season: a full clean including the underwater hull, polishing and waxing, and a check of sealant, fittings and seals.
Which mistakes should you avoid?
- Household abrasive cleaners on gelcoat. They leave the surface dull and rough.
- Working from the bottom up. Dirty water then runs over the clean areas.
- Letting soap dry in the sun. Work in sections and rinse as you go.
- High pressure on teak or on sealant joints.
- Letting waste water run into the water when cleaning the underwater hull.
Frequently asked questions about cleaning a boat
Which cleaner should I use on a fibreglass boat?
A pH-neutral boat shampoo is enough for most jobs. For stubborn streaks, use a hull or waterline cleaner. Avoid abrasive cleaners and strong degreasers, which dull the gelcoat.
How do I make dull gelcoat shine again?
Clean the hull thoroughly first. Then polish with a compound that suits the level of weathering, by hand or with a polisher on a low speed. Finish with a coat of boat wax.
Can I clean a teak deck with bleach?
Better not. Chlorine and bleach can damage the wood and discolour the seams. Use a teak cleaner and a soft brush, working across the grain.
What should I do about algae on the underwater hull?
Remove it as soon as the boat comes out of the water, while it is still soft. Work on a wash-down area that collects the waste water. A plastic scraper and a stiff brush help with growth that is stuck on.
In short: cleaning a boat
Work from the top down with fresh water, a pH-neutral boat shampoo and soft brushes, and rinse each section before it dries. Treat teak, acrylic windows and antifouling with care, and keep the pressure washer away from teak and seals. Finish fibreglass with polish and wax to keep it protected through the season.