Marinetalk is supported by its audience. When you purchase through links on our site, we may earn an affiliate commission. Learn more

How to Bottom Paint a Boat on a Trailer? – 5 Easy Steps

Fact checked by William Hart

how to bottom paint a boat on a trailer

A boat can be one of the most expensive investments of your life, and maintaining it requires more than just banknotes—you need knowledge, skills, and patience. So, how do you protect your vessel and preserve its value, especially the bottom that continuously submerges in water?

In this article, we’ll explain how to bottom paint a boat on a trailer in five steps; each comes with helpful tips that will assist you along the way. Read below for more details!

Table of Contents

How to Paint a Boat’s Bottom on a Trailer?


What to prepare

Bottom painting a boat while on trailer requires the following tools and materials:

  • Pressure washer
  • Boat soap (optional)
  • Tape
  • 80-grit sandpaper
  • Orbit sander
  • Hook scraper
  • Vacuum cleaner
  • Boat paint primer (or barrier coat paint)
  • Paint
  • Paint tray and paddle or paint shaker
  • Boat stand
  • Disposable gloves, goggles, and a mask

There are two basic types of bottom paint for boats: hard modified epoxy paint and copolymer ablative paint.

While ablative paint is for trailer boats that are frequently moved in and out of water, hard paint is not. Thus, opt for hard paint only if you float your aluminum boat all year round.

Step 1. Prepare the boat’s bottom


To begin, load your vessel on the trailer and clean its exterior to remove any mud and marine growth:

  • Slowly run your power washer over the entire boat
  • Take your time with the corners and curves
  • If necessary, apply some boat soap and scrub off any mud or algae

When the exterior is dry, run the masking tape following the waterline to mask off the area you will paint. In addition, cover onboard electronic devices, such as through hulls transducers.

How to identify the waterline of your vessel? Here are two easy ways:

  • Store your boat on the water for two to three days: After that period, you will notice a visible waterline on the boat’s hull. But what if you don’t have that much time for this project?
  • Check the owner’s manual: The owner’s manual usually contains the measurement of the boat draft—the part that submerges when your ship enters the water. The measurement is often in feet and starts from the hull’s bottom, such as 4′ 9″.

Step 2. Remove the old exterior paint


If you’re going to paint a boat bottom for the first time, skip this step. Otherwise, determine whether you should remove the old paint. You will need to strip it under the following circumstances:

  • The old vinyl paint is chipped and blistered: The new paint won’t adhere properly to an uneven and spotted surface. Even when it does, the coat will look flawed and lower the value of your vessel.
  • The old layers are too thick: Paint adds weight to a vessel; thus, layering more paint to the thick coats underneath will weigh down your boat. If you intend to build a boat for speed, minimize the layers of paint on its bottom.
  • The new paint is different from the old: You can layer ablative paint on top of hard paint, but not the other way around. So, quickly identify the type of old paint you have by running your fingers over it. Dried ablative paint will leave specks of dust on your fingers.

Once you decide to remove the paint, use a hook scraper to strip it off. You can also use a random orbit sander and 80-grit sandpaper for boat bottom paint.

Note: Put on your gloves, goggles, and mask before sanding bottom paint. Inhaling chemicals and sanding dust can cause injuries to your lungs and airway.

Step 3. Sand the boat’s bottom

Sanding boat hull is critical before painting. It removes imperfections and creates a fit surface that paint can adhere to.

Carrying out this step by hand is time-consuming. Instead, use a random orbit sander or a finishing sander to sand the entire surface. Some sanders have inlets for hooking up vacuum hoses. If yours has one, attach the vacuum hose to the sander before working.

When you finish sanding, wipe the entire bottom with a clean cloth to remove any remaining dust. If you don’t have a vacuum assisting you during the process, you might need to pressure wash the boat to blast away the dust and debris.

Step 4. Apply the primer or barrier coat

A barrier bottom coat will deter water penetration and facilitate paint adhesion. So, don’t skip this step.

You should use a brush or roller to coat the boat’s bottom with a thin primer layer. Be careful to paint evenly and avoid drippings. Read the manufacturer’s instructions to know if you need a second coat.

Step 5. Paint


Don’t dip your brush directly into the can to paint your pontoon boat! You must mix it before use. You can pour the product into a bucket and stir thoroughly with a mixing paddle for ten to fifteen minutes, but the best way is to use a paint shaker.

Then, transfer the paint to a tray and start painting the boat bottom with a brush or paint roller. You should begin from the waterline, slowly work your way downward, and coat the border carefully.

Some paint brands recommend using two barrier coats to create a more adhesive medium. So, don’t forget to read the instructions to know whether you should apply another coat.

  • Note: Stir the paint frequently during the process. You don’t want the pigment to sink to the bucket’s bottom.

When you finish painting boat bottom, quickly remove the painter’s tape and let the paint dry naturally. After that, lift boat off trailer to paint bottom’s missing spots. You can use a pair of boat stands for trailered boats or any boat lift systems you have to keep the vessel in place.

Finally, finish up the blank spots with the remaining paint. Feel free to mix extra paint if necessary. Wait until the coating dries and remove the boat stand.



How many coats of bottom paint should I put on my boat?

The answer depends on the types of bottom paints you use:

  • For hard paint, we recommend applying one to two coats. The thicker you layer hard paint, the more likely it will blister and crack.
  • For copolymer ablative paints, we recommend applying two to three coats. However, if you only land your vessel seasonally, one coat is sufficient.

Do I need bottom paint if I trailer my boat?

Yes, you do. Landing your boat in water and then trailering it put considerable pressure on the bottom’s gelcoat; thus, you need antifouling paint to protect it.

Besides, you must use the correct paint type. There are two basic types of anti fouling paint: Hard and ablative paint. The former loses its protectiveness when removed from the water for more than 72 hours; don’t use it if you store your boat on a trailer.

Meanwhile, ablative paint is softer and more flexible; even when it slowly wears away, its efficacy doesn’t decline, since a new paint coat will replace the old one. If you trailer your boat, you must use ablative paint for the boat bottom.

  • Note: You don’t need to paint the bottom if you store your boat above the water with a lift.

How often should I repaint the bottom of my boat?

It depends on the paint you use and the frequency of water contact. High-quality paint for boat bottoms can last up to two years. But if you use your vessel a lot, whether for fishing or just cruising, an annual recoat is likely necessary.

Do I need to paint my vessel’s bottom?

If your boat is exposed to water a lot, bottom painting is necessary to preserve the performance of the vessel, especially its fuel efficiency.

However, painting the boat’s bottom can cause several problems:

  • The process is tedious, time-consuming, and expensive.
  • You need to re-examine and repaint the coat every one to two years.
  • The paint can weigh down your vessel and affect its performance.

So, if you only float your boat occasionally and store it on a boat trailer most of the time, don’t bottom paint it. Instead, consider applying one or two layers of protective wax. The wax will require less maintenance and keep the boat’s value when you resell it.

How much does it cost to paint a boat’s bottom?

Boat services often charge by foot. For instance, you may see recoating prices of $28-$31 per foot, with the latter rate applying to larger boats. The cost may also increase for first-time paintings and vary depending on the hull material.

You can reduce the cost significantly by doing it yourself. You will only need to pay for the tools and materials, which are affordable. For example, TotalBoat’s AlumiPaint AF for boat bottoms costs $200 per gallon, which covers 500 square feet.

For more details on this topic, click here to learn “Average Cost to Paint a Boat”


That wraps up our guide on how to bottom paint a boat on a trailer. A paint job is crucial to preserving the beautiful state of your boat’s bottom and preventing the growth of marine organisms. So, kickstart the project as soon as you can.

Don’t forget to save this guideline, so you can refer back to it in the future and share it with other boat owners. Thank you for reading!

5/5 - (2 votes)