Updated: Apr 18, 2022
What is Bottom Paint and What is its Purpose?
Antifouling paint, also known as bottom paint, is a paint that is applied to the underwater portion of a boat's hull in order to thwart off any marine life such as barnacles, weeds, and other organisms from attaching themselves to the bottom of your boat. If you have a wooden vessel, then these organisms would actually begin to eat away at the hull.
The way this works is that most bottom paints contain what is called a biocide, which more often than not is made up of copper.
Today however, there are more environmentally friendly antifouling paints that contain little to no copper at all.
What is the best bottom paint for a boat?
The answer to this question is a bit vast, so let’s first break down the three main categories that exist for antifouling paints.
For more info on this topic, read our detailed review article on the Best Boat Bottom Paints.
Ablative, also known as self-polishing, paints are designed to slowly wear away in order to expose fresh biocide as your boat glides through the water.
The main advantage to this is that as long as paint is still remaining on the hull, then you know that it is still working to prevent the growth you don’t want, as long as you're using the boat frequently.
A secondary benefit to this style of bottom paint is that you don’t really have to deal with any buildup of old paint that can be very difficult to remove once that time comes.
The disadvantage to ablative bottom paints is that if your boat remains stationary for long periods of time, it is generally less effective due to the lack of self-cleaning that takes place with water movement.
However, these are also not ideal for fast-moving vessels due to the fact that the ablation process would accelerate and cause the paint to come off much quicker.
The copper biocide is what wears away over a period of time rather than the paint itself with hard bottom paints, which are also referred to as hard modified epoxy or non-sloughing paints. This process happens by allowing the water to penetrate deeper into the paint until the complete depletion of all biocide has happened.
Hard bottom paints are more ideal for faster moving boats because they create a very strong and hard coating that does not wear away and holds up very well.
While they do perform very well for faster boats, it becomes very difficult to remove this hard coating once all of the copper has been depleted. This makes way for a very difficult and messy process to remove when the time comes, especially if there have been multiple layers added through the years.
Eventually, the paint will become so thick, that it will begin to peel and crack and it will be absolutely necessary to perform a complete stripping of the entire hull bottom
Hybrid, aka semi-hard ablative paints, are exactly as you would imagine in your mind. They are a match between ablative and hard paints, in that they provide the benefits of both in a single product.
Hybrid bottom paints create a smooth yet hard surface and will resist the organism buildup, while at the same time can tolerate faster speeds and repeated haul-outs without sacrificing the protection.
The best resource for finding out which paints are recommended for your area is to speak to a local boatyard manager. They will be experienced and have a vast amount of knowledge for you to make the right decision.
How often do I need to paint the bottom of my boat?
This is certainly the most common question when it comes to this subject, and there is no one perfect answer. However, generally speaking, you should have a new layer of bottom paint added once per year, but it is not uncommon for some paints to still be effective for up to 2 years.
A few questions that should be asked to get a more accurate answer to this question are the following:
What type of paints are you using?
How often do you use your boat throughout the year?
Where and how are you storing your boat when not in use?
If you are keeping your boat in the water or are using it very frequently, then it is wise to have it checked every year to determine whether you are in need of a new application. If you keep your boat properly washed and stored out of the water, then you may be able to get away with every other year.
Does bottom paint slow down a boat?
The quick and short answer to this question is that yes it can. This is a highly debated topic within the industry. If you have a professional company do this job for you and they get a nice smooth bottom paint, then you will hardly notice any loss of speed.
However, the more layers of paint that get added to the hull over time, and if the boat is not getting much use, then you will undoubtedly begin to notice significant drag taking place.
On the other hand, ablative antifouling paint is designed to shed itself, and this may cause the paint job to get a bit rough as this process takes place, which in turn may cause you to feel some loss of speed.
Proper maintenance practices are the key here. If you keep up with the maintenance, then this will ensure that speed loss is very minimal.
What are the most popular brands of boat bottom paints?
Here are a few of the most popular brands to look for:
Do I need bottom paint on my boat?
It is not absolutely necessary for all boats to get the bottom of the hull painted with antifouling paints. For instance, if you do not keep your boat in the water for long periods of time, it is stored on a trailer, lift or dry storage facility, then you most likely do not need to paint the bottom of your boat.
In this situation, keeping your vessel washed down and maintaining it with a routine detail program that utilizes a high quality wax protectant will do just fine.
On the flip side of this, if you keep your boat stored in the water year-round or at least for most of the boating season, then it is highly recommended if not mandatory that you do take the step to get a bottom paint put onto your vessel especially when kept in saltwater due to high marine fouling growth.
How much does it cost to have your boat bottom painted?
Secondary to whether you should or should not bottom paint your boat's hull, is knowing just how much this will cost. There is no exact price point that answers this question, but generally speaking, the price will be determined by the size of your vessel and the type of paint being used.
You either have the option to DIY or to have a professional company do this service for you.
Going the DIY route will be the most cost effective route, but will certainly be much more time consuming.
If you so choose to take on this project yourself, then you will want to further educate yourself on the steps involved to properly protect yourself and find out what equipment you will need to do the job right the first time. You can go here to learn more about that.
For the purpose of this article, we would encourage you to hire a professional that is highly experienced in this line of work. Start calling some of your local marine service businesses and get some quotes to get a better feel for just how much this will cost for your vessel.
Overall, if your boat is going to be spending the majority of its time in the water, then it is highly recommended that you make bottom painting a routine part of your boat’s maintenance.
This will ensure that your hull is well protected from accumulating unwanted marine growth that can damage your boat's hull, will help increase the lifespan, and will improve fuel economy.