How to Install a Boat Trailer License Plate Mount

Installing a boat trailer license plate mount is a simple job that requires a bracket, stainless steel hardware, and a few basic tools. Most setups involve drilling pilot holes, securing a trailer license holder with bolts, and attaching your plate so it stays visible and secure on the road.

Around 100 million Americans go boating every year, according to the National Marine Manufacturers Association, which means millions of trailers need reliable license plate brackets that can handle regular towing and water exposure.

Here at Owens & Sons, we build custom aluminum boat trailers, supply trailer parts, and handle repairs nationwide, so we know how important a properly mounted plate is for safety and compliance.

Tools and Parts You Need Before You Start

Getting the right tools and parts in place makes installing a boat trailer license plate mount quick and straightforward. A basic setup includes:

• Trailer license holder
• Stainless steel bolts
• Nuts
• Washers
• Drill
• Wrench or socket set

Stainless steel hardware is the best choice for boat trailers, as regular steel can rust quickly, especially after repeated exposure to water. Stainless options hold up better and reduce the need for frequent replacements over time.

A quality drill with the correct bit size is also important. Clean, accurate holes help the license plate brackets sit flush against the frame. That reduces movement and prevents long-term wear on the mounting points.

At Owens & Sons, we see many avoidable issues during trailer repairs caused by poor hardware choices. Using durable parts from the start keeps your mount secure and helps your trailer perform reliably on every trip.

Step-by-Step: How to Install a Boat Trailer License Plate Mount

You should start by choosing a mounting location at the rear of your trailer. The plate should be clearly visible and not blocked by the boat, lights, or other equipment. A flat section of the frame usually works best.

Next, mark your hole positions using the bracket as a guide. Keeping everything level at this stage helps avoid a crooked plate later. It’s important to double-check spacing before moving on to drilling.

Drill pilot holes using steady pressure and the correct bit size. This step is especially important on aluminum trailers, where clean holes prevent damage. Once drilled, line up the trailer license holder and insert your bolts.

Tighten everything using washers and lock nuts to keep the mount secure. Then, attach the plate, check alignment, and give it a quick shake test. Here at Owens & Sons, we always stress secure installs to prevent vibration damage during towing.

What Screws Do I Use to Mount a License Plate?

The best option for mounting a boat trailer license plate mount is stainless steel bolts with matching nuts and washers. A common size is 1/4″-20, which fits most license plate brackets and provides a secure hold.

As noted above, stainless steel is ideal for marine use because it resists rust and corrosion. Boat trailers are often exposed to water, so using the right material helps avoid early failure and keeps the mount intact.

Self-tapping screws can be used in some cases, but they are less reliable over time. Vibration from towing can loosen them, especially if the trailer is used frequently or on rough roads.

Adding washers helps distribute pressure and reduces stress on the bracket and frame. We recommend secure bolt-through setups since they hold up better and reduce the risk of plates coming loose during transport.

What Size Drill Bit for License Plate Bolts?

The correct drill bit size depends on the bolts you are using. For a standard 1/4″ bolt, a slightly smaller pilot hole, such as 3/16″, works well and allows the bolt to fit tightly and securely.

Pilot holes are important because they guide the bolt and prevent damage to the trailer frame. Skipping this step can lead to uneven holes or difficulty when tightening hardware.

When drilling into aluminum, steady pressure and a sharp bit make a big difference. Oversized holes can weaken the mount, while rough drilling can affect how the bracket sits against the surface.

At Owens & Sons, precision matters in every part of trailer setup and repair. Taking the time to match your drill bit to your hardware ensures a clean install that holds up under regular towing conditions.

Frequently Asked Questions

Can I Install A License Plate Mount On Any Trailer Frame?

Most trailer frames can support a boat trailer license plate mount, including aluminum and galvanized steel. The key is choosing a flat, stable area that allows secure drilling and proper visibility from the rear.

Should I Use A Backing Plate For Extra Support?

A backing plate can improve durability, especially on thinner frames. It helps spread the load and reduces stress around the mounting holes, which is useful for trailers that see frequent use.

How Do I Protect The Mount From Corrosion?

Rinsing your trailer after saltwater use is the first step. Using stainless steel hardware and corrosion-resistant license plate brackets also helps extend the life of the setup.

Can I Mount The Plate On The Trailer Light Bracket?

Some trailers allow this, especially if the light bracket includes a built-in trailer license holder. Make sure the plate stays visible and does not block the light output.

What Causes License Plates To Crack Or Break On Trailers?

Vibration is the main cause. Loose hardware, missing washers, or poor mounting locations can lead to stress on the plate, eventually causing cracks or complete failure.

Get the Right Parts for Your Trailer Plate Installation 

As we’ve highlighted above, a secure boat trailer license plate mount keeps your trailer compliant, visible, and ready for the road. With the right tools, hardware, and approach, trailer plate installation is quick and reliable, even for first-time installs. Paying attention to materials and fit helps prevent issues down the line.

At Owens & Sons, we supply high-quality trailer parts, build custom aluminum trailers, and handle repairs nationwide. If you need a durable mount, replacement hardware, or expert support, our team is ready to help. Contact us to get the right setup and keep your trailer performing at its best every time you tow.