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How Are Boat Trailers Measured?

A photo of empty boat trailer on the pier.

If you are planning on moving your boat, or maybe you are thinking of buying a new boat, it is essential to know the correct measurements of the boat. But it is equally important to know the size of the trailer if you are to ensure your boat fits snugly on the trailer, as this is critical for safe transport.

Because the best boat trailer is one that fits, you must have the dimensions (and weight) of the boat to know which trailer would suit your intended purposes.

Related: 15 Parts of a Boat Trailer

How Are Boat Trailers Measured?

Trailer dimensions define the distance of the boat at its maximum measured width and length. The RVIAdefines it as the “usable floor plan length,” – which means the trailer tongue (or coupling mechanism) and the rear bumper should be excluded from the measurement.

These are the steps to measure a boat trailer –

Measuring the Length

A photo of trailer boats in the sand.

The trailer’s length can be measured using a tape measure – along the trailer’s centerline.

Length overall (LOA) is measured from the top/tip of the boat’s bow– unbent, to the stern or the back of the boat or watercraft. When measuring, include any rear deck extensions (which are also known as platforms). Other attachments are not included when measuring, as most of these support brackets are removable.

The boat you measure for will need to fit within the measured length space of the trailer. If the boat exceeds the trailer’s length (and sticks out beyond the trailer), it could be dangerous to drive on the road.

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Measuring the Width

The width of the trailer is the point with the greatest outside width. It varies from trailer to trailer and may include the distance from fender to fender (for trailers with tires on the outside of the frame) or from the side-rail to side-rail. Your boat must fit on the trailer correctly and snugly.

Measuring Vertical Distance

A speed boat park on the boat trailers at beautiful sunset environment.

Knowing the vertical height of a boat trailer, I learned, was important when backing the trailer down a boat launch ramp. To measure the vertical distance, measure starting at the top of the trailer to the ground – this is the trailer’s vertical height.

This is essential because a trailer that sits higher off the ground will need to back farther down the ramp than a trailer with a smaller vertical height.

Finding the GVWR – Gross Vehicle Weight Rating

Look at the trailer’s placard, which is attached to (or engraved on) the trailer in differing locations, depending on the manufacturer. The placard will provide the Gross Vehicle Weight Rating (GVWR), which represents –

Maximum load-carrying capacity is the gross vehicle weight rating (GVWR) less the weight of the empty trailer.

The total weight of your boat, engine, fuel, water, and gear must not exceed the trailer’s maximum load-carrying capacity. Overloading can cause serious injury or property damage.”

How Is Trailer Tongue Length Measured?

A white yacht in the trailer on a white background.

The tongue of a boat trailer is the part of the boat trailer that extends beyond the trailer’s main body to the coupler. These devices are used to hitch the boat trailer to the towing vehicle.

Boat Trailer Frame Material Options

Boat trailers are manufactured using different materials. The material that is used should not only offer appropriate support for the vessel but is also suitable based on where you will launch your boat.

While no two companies use the same mix or combination of materials, the most common materials used to manufacture boat trailer frames are –

  • Aluminum I Beam – great for use in saltwater; however, aluminum’s lightweight leaves it vulnerable to bending or flexing. Terrific strength to weight ratio and is not prone to rust.
  • Tube Steel – great looking (and can even be painted to match the boat’s color), but water can get trapped inside the tubular farm and cause rust from the inside out.
  • C Channel Steel – this is strong and offers no worry of rusting from the inside. A boat trailer frame can be manufactured from steel specifically to be used in saltwater.
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How Much Length Does A Trailer Add To A Boat When transporting?

In general, a boat trailer tends to add about two feet to the boat’s actual length.

How Much Does A Boat Trailer Weigh?

Two trailer for boats on the beach with golden sunset.

A trailer for a fishing boat can weigh upwards of more than a ton without a payload! The average weight for a boat trailer ranges around 600 pounds. A boat trailer’s weight will depend upon its designed and intended use.

Here are a few examples of trailer types and their weights

Trailer Type Avg. Empty Weight
Also Known as Dry Weight
GVWR (lbs.)
Maximum Total Weight
Avg. Load Capacity –
  Weight of Cargo
Canoe/Kayak Trailer 200 lbs. 200 lbs. to 800 lbs. 200 lbs.
Jet Ski Trailer 300 lbs. 800 lbs. to 3,000 lbs. 1,500 lbs.
Small Fishing Boat Trailer 600 lbs. 900 lbs.  to 6,000 lbs. 2,700 lbs.
Large Boat Trailer 2,200 lbs. 800 lbs.  to 3,000 lbs. 11,400 lbs.

Understanding the Trailer’s VIN (Vehicle Identification Number)

A trailer VIN is its unique identifier that is usually imprinted somewhere on the trailer’s framed metal. The Vehicle Identification Number is often found in the vicinity of the trailer’s coupler. The NHTSA of the US Department of Transportation requires all trailers which will be used on the road to have a Vehicle Identification Number that has 17-digits.

The Vehicle Identification Number’s digits actually encode relevant information. The sixth and seventh characters within the VIN would reveal the trailer’s length.

State Regulations Regarding Boat Trailers

A 4x4 black car pulls blue-white cabin motor boat on trailer.

Before I towed my boat, it was recommended that I familiarize myself with the regulations and rules for trailers – for every state my journey passes through. The information regarding trailered boats is available in each state’s Department of Transportation.

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What Is The Widest Trailer One Can Tow?

In most states, a boat trailer’s width cannot exceed 8 feet, six inches – or 102 inches. Trailers that exceed this established limit are considered a wide or oversized load – and therefore subject to additional regulations – like permits or flags. Some wide-load trailers are restricted to roads only on a weekday. The maximum height limit is generally 102 inches.

Trailer Maintenance Information

A truck towing a boat on the interstate.

Boat trailers and other vehicles designed for towing purposes are typically required to have regular and frequent maintenance checks and tune-ups. Before heading out to tow your boat, be certain to check the following –

  • Tires
  • Brakes
  • Hitch
  • Wiring, etc.

The Take-Away

Many automobiles, vans, SUVs, and trucks are now built to specifically equip the vehicle with the capacity to tow. The trailer that you will need to tow a boat depends on the many factors noted above. In addition, there are many types of trailers from which to choose, so be sure to complete enough research (i.e., due diligence) before making the final purchase.

The right-fitting boat trailer offers safe transportation when moving the vessel. But it also helps to save money from repairs to the bottom of the boat by avoiding fees charged for docking at a marina. A boat trailer also offers you the option of moving a boat to safe, dry land before a storm hits.

The correct fitting boat trailer will protect your investment – giving you years of safe enjoyment.