Sailboat Bottom Cleaning - Complete DIY Guide

Sailboat Bottom Cleaning: Complete DIY Guide | Life of Sailing

Last Updated by

Daniel Wade

June 15, 2022

Sailboat bottom cleaning is an essential part of regular hull maintenance, but it doesn't have to be a serious hassle.

Sailboat bottom cleaning can be done in or out of the water. The most important tools include marine gloves, various scrapers, and brushes. A coat of high-quality bottom paint can reduce cleaning intervals and marine buildup.

In this article, we'll go over how to clean a sailboat bottom in or out of the water. We'll cover the best methods and give you a rundown of all the tools you'll need to do the job. Additionally, we'll go over the importance of bottom paint and the best methods to reduce the headache of hull maintenance.

We sourced the information used in this article from sailors with bottom cleaning experience. Additionally, we gathered facts about hull cleaning from reliable sailboat maintenance guides.


Table of contents

What Happens to a Sailboat Hull in the Water?

A clean sailboat hull doesn't stay clean for long, but any skipper can tell the difference between a freshly scraped hull and a neglected bottom. As soon as you drop the boat in the water, marine gunk starts to slowly accumulate on all submerged surfaces.

First, bacteria and microorganisms start to accumulate and build up a slime. Anti-growth paints slow this buildup, but it eventually overpowers the paint. At this stage, a simple hosing down could do the trick. But over time, the slime forms a protective layer onto which larger and more sensitive organisms can begin to thrive.

Within a month or two, even the most well-maintained sailboat bottom will start to accumulate your local species of barnacles, mussels, and sharp sea trash. The bottom is now its own micro-ecosystem.

Soon, all of that annoying and injurious sea garbage will begin clogging intakes, exhaust ports, drains, and jamming up rudder components.

How Often Should You Clean a Sailboat Bottom?

Bottom cleaning should be done regularly, regardless of how you use your boat. That said, it's a more urgent task for some sailors who get underway often.

People who cruise regularly or over long distances should clean the bottom once every month or two, whereas the twice-per-year sailor can get away with a biannual cleaning.

The Importance of Sailboat Bottom Paint

Bottom paint is specially formulated to slow or stop the growth of marine life. Traditionally, 'red lead' paint was used to inhibit barnacles and other gunk from taking refuge on the hull. Red lead is just that—red paint with high lead content. Lead is poisonous to marine life, and it's extremely effective at preserving the bottom.

Red lead comes with hazards, and it's difficult to obtain in some areas. Today, its use is limited to wooden boats and historical restorations.

In the 21st century, numerous less toxic paint alternatives exist. They're costly, but modern bottom paints can last for years without significant repairs.

It's essential to keep your hull covered in a strong layer of bottom paint, regardless of the age or condition of the vessel. High-quality bottom paint can drastically reduce hull growth and cleaning intervals, which is why it's a key priority for long-range cruising skippers.

Why is Bottom Cleaning Necessary?

Bottom cleaning is absolutely necessary if you want your boat to work well and last a long time. Marine life grows rapidly on sailboat hulls, and it can add weight to your hull and cause damage.

The biggest issue with marine growth is drag, as it adds a rough texture to an otherwise smooth sailboat hull and slows it down. Additionally, marine life can seize rudders and clog seacocks.

What Happens if You Don't Clean the Hull?

Here's a typical scenario to consider. Let's say that your sailboat has been sitting in a slip at a marina for about a year, and you decide to take it out sailing on the water. You can see an unseemly buildup of marine gunk on the bottom of the hull, but you decide to go sailing anyway.

You start the engine to pilot the boat out of the slip, and before long, your diesel inboard is overheated, and you're left dead in the water and drifting. It's not a good situation and a potentially expensive mistake too.

The reason the engine overheated is that barnacles and sea plants clogged the cooling water intakes on the bottom of the hull. This is why powerboats are pulled out of the water after use and why frequent bottom cleaning is necessary.

Can You Clean a Sailboat Bottom in the Water?

Absolutely, many people clean the hull of their sailboat while it's still in the water. In fact, you may not even have to get in the water to do it. There are special brushes available that allow sailboat owners to clean the bottom from the dock.

These brushes have a long angled handle that allows you to reach under the boat from above. This method works great for round-bottom boats, though special care must be taken to clean the keel and the rudder.

If you're willing to get in the water, you can also clean the bottom using scuba gear or a snorkel. If you do, be sure to choose a safe location that doesn't have any marine traffic.

How to Clean a Sailboat Bottom

Cleaning a sailboat bottom is pretty self-explanatory, and anyone can do it in a reasonable amount of time. That said, you'll need the proper tools and techniques to do it safely and effectively.


Here is a list of the best tools to grab before cleaning the bottom. You don't necessarily need them all, but it's best to have a full set of implements at your disposal.

It's also a good idea to buy purpose-made marine tools, as you need the right scraper thickness to avoid damaging the hull. If you have a friend with marine tools, borrow them or bring them along to a hardware store to find comparable scrapers.

1. Gloves

Gloves are an important and often overlooked tool for bottom cleaning. Ever try to walk along a rocky shoal barefoot? You probably didn't get far. Barnacles and shells are hard and extremely sharp, and a slip of the hand can result in a trip to the urgent care clinic and a few stitches.

Specially-made marine gloves allow good mobility and excellent protection from sharp marine growth.

2. Scrapers

You'll need scrapers of various kinds to remove the harder gunk such as barnacles and mussels. These come in multiple shapes and sizes. You should have more than one size available to help clean odd spaces, such as around your propeller shaft and rudder assembly.

3. Scrubbers

Scrubbers are useful tools for using outside the water. They're usually large, round brushes that attach to a motor or a power drill. While scrubbers usually aren't useful for removing severe growth, they're excellent for finishing the hull after scraping the stone-like barnacles off.

4. Pressure Washer

A pressure washer with a specialized marine nozzle is an excellent choice for getting work done quickly. Larger boats benefit most from a pressure washer, as it can blast off all kinds of marine growth. Just be careful, as the jet is extremely powerful and concentrated.

5. Brushes

Brushes are an essential tool for cleaning a sailboat bottom. There are literally hundreds of marine brushes to choose from, and they're available in all shapes and sizes. Some brushes are handheld and small, while others have long handles for dockside cleaning.

Bottom Cleaning in the Water

Bottom cleaning in the water is the least costly way to do it, as you don't have to pay for a boat crane or a place to park your trailer. Plus, with no jack stands in the way, you can clean the entire hull.

First, make sure you're a good swimmer. Even if you don't get in the water, it's essential to be prepared if you fall in. The most common way to clean the bottom in the water is to grab some goggles and a snorkel and go for a swim.

Start by scraping the larger marine growth with a scraper. If there isn't any hard growth, such as mussels or barnacles, you can begin with a heavy brush and start removing the gunk.

Use extra care around intake ports and moving parts, as it's especially important that these items be clean.

Check Anodes

Most sailboats have bolt-on sacrificial zinc anodes around certain metal parts. These anodes 're-route' corrosion. They corrode instead of your metallic boat parts, but once they get badly pitted, they stop functioning. Check the anodes and make sure they're in good condition. If not, replace them promptly.

Out-Of-Water Sailboat Bottom Cleaning

It's easy to clean the bottom of a sailboat out of water and generally less physically taxing. Here, you can use power tools (such as a power drill scrubber) and pressure washers to expedite the process.

Use the same care to avoid scraping off paint and damaging the hull. Once out of the water, you can inspect the condition of the bottom paint and repair hull damage.

General Rules of Sailboat Bottom Cleaning

Bottom cleaning is a regular and relatively unpleasant task, but it doesn't have to be difficult. Here are a handful of helpful tips to make sailboat bottom cleaning as safe and easy as possible.

1. Pull the boat out of the water if you can.

Pulling the boat out of the water makes life a whole lot easier when you need to clean the bottom. It allows you to work on land and get a full, well-lit 360-degree view of the hull.

2. Avoid harsh chemicals (if possible).

There are lots of quick-fix chemicals available to make hull cleaning easier, but it's best to consider the potential consequences of using them. Many of these chemicals contain harsh compounds and solvents, which are harmful to your health and damaging to the environment.

It doesn't take much to cause problems. Just a pint of petrochemicals can contaminate an acre of water or more, and a gallon of chemicals can contaminate over a million gallons of water. When possible, use biodegradable chemicals and safe paints.

3. Use secure boat jack stands.

If you pull the boat out of the water, be sure to use high-quality boat jack stands that are rated for the weight of your vessel. Take into account the extra weight of tanks and additional items aboard. Also, ensure that the jack stands are in good condition and not corroded.

4. Buy better brushes.

Buying high-quality hull brushes can make a world of difference when cleaning the bottom. High-quality brushes are built better and less likely to damage the bottom of your boat or scrape off your paint. Also, avoid using brushes that aren't designed for hull cleaning.

5. Clean the hull in a safe location.

If you must dive under the boat while it's in the water, be sure to do so in a safe area without marine traffic. Use a flag and markers to alert other boats that you're in the water, as they may not be able to see you when motoring around.

Sailboat Bottom Cleaning - Complete DIY Guide
Daniel Wade

Daniel Wade

I've personally had thousands of questions about sailing and sailboats over the years. As I learn and experience sailing, and the community, I share the answers that work and make sense to me, here on Life of Sailing.

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