bing tracking image

4 Crucial Choices You'll Make when Buying a Boat Trailer

The 4 Crucial Choices You'll Make When Buying a Boat Trailer

When it comes to spending a day on the water, your boat is only half the equation. You'll also need a way to transport your boat from dry land to your preferred body of water—which is where a trailer comes in.If you're in the market for a boat trailer, you've probably wondered what size trailer you even need for your boat. How much longer than the boat should it be? How should the boat sit on the trailer? There may also be a few questions you haven't thought about yet. Will you go with an aluminum or steel frame? Bunks or rollers? What kind of suspension should you get?Below, we'll dive into what your options are in the big wide world of boat trailers, and we'll help you figure out what you should be on the lookout for, whether you're building a custom boat trailer or looking for a used trailer online.In this article:
  • How Big of a Boat Trailer Do You Need?
  • Painted vs Galvanized Steel vs Aluminum Trailers
  • Suspension: Leaf Springs vs Torsion Beams
  • Bunks vs Rollers

1. How Big of a Boat Trailer Do You Need?

It's important you get the "goldilocks" trailer for your boat. This means the trailer has to be just right in terms of size and weight capacity.If you end up with a trailer that's too big or too small, you may not be able to achieve the proper tongue weight to safely tow your boat (more about tongue weight later). A good rule of thumb is that your trailer should be slightly longer than your boat (at least 2' but sometimes as much as 6') to allow the trailer to turn and to make sure your boat sits on the trailer properly. And it needs a weight capacity sufficient to haul the "wet weight" of your boat.So how exactly do you measure your boat to determine the right trailer length and width? How do you calculate the necessary weight capacity? We'll go over this below.
Car towing boat trailer

Measuring Your Boat Length & Width

You'll need to measure your boat length and width to get the right size trailer, but how you measure your boat is important—it's not as simple as using the manufacturer's listed LOA (length overall). In fact, this will give you the wrong measurement!Why? Manufacturers typically list the LOA as the entire length of the vessel, including additions like swim platforms and bow pulpits. For the purpose of measuring your trailer, you'll usually just include parts of the boat that are actually supported by the trailer, such as:
  • Bow eye to transom (sometimes bow eye to drain plug) - Typically the most important measurement for length
  • Chine beam (fender to fender) - Typically the most important measurement for width
  • Some boats may require specific measurements; for instance, a triple tube pontoon boat may have a center tube that extends farther than the outside pontoons, in which case your trailer will need to accommodate the extra length. (In general, pontoon trailers should be 3' - 5' longer than your pontoon tubes.)
When ordering a custom trailer, the manufacturer will let you know what other measurements you'll need to take. But in general, the idea is that your boat should be positioned for maximum support on your trailer. (Keep reading to find out what that looks like.)
Bow eye to transom plug
Length Overall
Chine beam

How Should a Boat Sit on a Trailer?

A properly sized boat trailer should be about flush with the transom, allowing the transom to hang off the bunks or rollers by as much as 1 ft. The hull should be centered on the trailer with its weight evenly distributed across the bunks or rollers, both side to side and front to back.At the front, the bow eye should reach the winch post, but make sure the bow roller does not support the hull (it's okay if it touches, but it shouldn't support the boat's weight). The winch should be horizontal to the bow eye so that it pulls straight across, not up or down.For a single-roller bow stop, place the bow stop above the bow eye. For a double-roller bow stop, place the upper roller above the bow eye and the lower roller below it. You should also have sufficient tongue weight at the front of the trailer to prevent swaying on the road. Which brings me to my next point...
Boat On Trailer Diagram

How Do Determine the Wet Weight of Your Boat?

Making sure your trailer can support your boat weight is, of course, pretty important. Right off the bat, let's be clear that we're NOT talking about dry weight, as provided by your boat manufacturer. Rather, your trailer needs to support your boat's "wet" weight—the true weight of the load on the trailer. This includes not just the boat itself but anything else that will be weighing down your boat while it's being towed.When determining the capacity needed for your trailer, consider the following:
  • Boat weight
  • Motor
  • Batteries
  • Fuel (approx. 6 lbs/gallon)
  • Water (approx. 8 lbs/gallon)
  • Gear (typically about 10% of total boat, motor, and liquid weight)
Boat On Trailer Diagram
Smaller boats up to about 3,300 lbs or about 22' - 23' can usually get by with a single-axle trailer. Larger boats will require a tandem axle trailer. A good rule of thumb when estimating how much weight capacity your trailer needs is to add up your loaded weight using the factors listed above, add 15%, and choose a trailer that can handle this weight.The trailer's capacity isn't the only thing to consider; you also have to keep your tow vehicle's weight capacity in mind. Check your vehicle's owner's manual (most are available online) for your tow capacity. You can also perform a quick calculation:
  • On the white sticker inside your vehicle's door, take a look at your GCWR (Gross Combined Weight Rating). This is the maximum weight of your loaded vehicle + your loaded trailer.
  • Subtract your GVWR (Gross Vehicle Weight Rating) from the number above. Your GVWR is the maximum weight of your loaded vehicle.
  • The resulting number is the maximum loaded trailer weight you can tow.
Maximum Loaded Boat Trailer Weight
For a closer look at average boat and trailer weights, check out our article here.

How Do You Determine Tongue Weight on a Boat Trailer?

Tongue weight is the downward force you're putting on the hitch ball, plus the weight of any gear behind the rear axle of your vehicle. Maintaining proper tongue weight is crucial to safely towing a boat, since having the proper percentage of tongue weight will help prevent dangerous trailer sway. The ideal tongue weight for a boat trailer is about 5-7% of your total trailer weight—much less than the average travel trailer tongue weight. This is because the majority of the weight is at the back of a trailer where the engine is, so the weight will sit behind the rear axle.To determine your boat trailer tongue weight, you can use a scale like this one from Sherline or the Bluetooth-enabled HaulGauge. You can also use one of the other methods outlined in our help article, Determining Trailer Tongue Weight.Many boat trailers also allow for axle adjustment to achieve the proper tongue weight. If your tongue weight is too light, you'll need to move the axle farther away from the trailer tongue toward the back of the trailer. If your tongue weight is too heavy, you'll need to move the axle forward toward the front of the trailer. For a more in-depth look at positioning trailer axles, check out our article here.
Boat Trailer Tongue Weight

2. Painted vs Galvanized Steel vs Aluminum Trailers

There are several factors to consider when it comes to selecting the material your boat will be made of. Are you going to be in freshwater or saltwater? Are you boating offshore in southern tropical environments or in colder, northern waters, where the temperature slows corrosion?
Painted Steel Boat Trailer

Painted Steel

Painted trailers are generally the most cost-effective option. They also tend to be visually appealing off the bat and can even match your boat color (which, let's face it, just looks pretty cool). Keep in mind that these are not saltwater-friendly trailers—you'll want to stick with freshwater use. Maybe you have a small john boat, or you won't be launching often and don't want to invest a lot in a boat trailer. In this case, a painted steel trailer may be perfect for you. Just keep in mind that the paint will chip and fade over time, and your handsome boat trailer won't age with quite the same grace as the other options on this list unless you regularly repaint and maintain it.
Galvanized Steel Boat Trailer

Galvanized Steel

Galvanized steel trailers are great for use in either freshwater or saltwater due to their corrosion resistance. Rather than feature an exterior protective coat like those on painted steel, galvanized steel is hot dipped in molten zinc for superior protection. These trailers will cost more upfront, but you'll get more use out of one than you would a painted steel trailer (and if you're launching in saltwater and want a steel trailer, there's no question it needs to be galvanized). Many boaters don't find that galvanized looks as nice as aluminum or painted steel, but what this metal lacks in looks it makes up for in utility.
Galvanized Steel Boat Trailer

Aluminum

Aluminum trailers can be used in any environment, but they're especially ideal for saltwater due to their superior corrosion resistance. They're also lighter, which is great in terms of not burdening your tow vehicle with extra weight. Because they offer better corrosion resistance than painted or galvanized steel, they tend to maintain their good looks the longest. (Incidentally, they're also typically the highest priced trailer type.)

3. Suspension: Leaf Springs vs Torsion Beams

When you buy a new boat trailer, you'll typically get the choice between leaf spring and torsion beam suspension. Which is best for you? It mostly depends on whether you're willing to spring for an upgrade or not.
Leaf Spring SuspensionLeaf springs are attached either over or under the axle (they're either overslung or underslung). This is the most common and most cost-effective suspension type and usually comes standard on trailers.
Pros
  • Lower cost upfront
  • Easy to repair
  • Low cost to change out components
  • Promotes even tire wear (especially on multi-axle trailers)
  • Equalizers distribute trailer weight evenly over axles
  • Better on uneven surfaces
Cons
  • More frequent repairs needed
  • More susceptible to rust, especially for saltwater applications
  • Metal on metal design is noisier and wears faster
  • More moving components to wear and require replacing
  • Bouncier ride when empty
Overslung vs Underslung Trailer Axles
Torsion Axle Suspension Torsion axles provide suspension via thick rubber cords rather than metal springs. The cords reside in the axle itself, rather than over or under it. This type of suspension is usually considered an upgrade from the standard leaf springs.
Pros
  • Typically last longer - fewer components to wear or rust
  • Better for saltwater applications
  • Quieter, smoother ride with no metal on metal friction
  • More stable (torsion axles are bolted or welded to the trailer)
  • Essentially maintenance free
  • Wheels operate independently (if you blow a tire on your triple-axle trailer with torsion suspension, you can drive on 5 wheels to the next rest stop)
Cons
  • Costs more upfront
  • Can't repair; must completely replace
  • No equalizer; doesn't distribute weight or impact among all axles
  • Increased tire wear, especially on multi-axle trailers
Torsion Trailer Axle

4. Bunks vs Rollers

Another choice you'll have when picking out your new trailer is the choice between bunks and rollers. The best choice for you depends on what your boat, your launch site, and your price range.
BunksBunks boards, which are typically wood covered with carpet, allow your boat to slide on and off your trailer when you launch.
Pros
  • Less expensive upfront
  • Lighter, with higher weight capacity
  • Don't require much maintenance, since they're just wood and carpet
  • Friction provides greater trailer support
Cons
  • Must be submerged to launch/retrieve boat
  • Harder to launch on bad ramps or in poor conditions
  • Frequent submersion can lead to quicker corrosion
Boat Trailer with Carpeted Bunks
RollersRollers are your other option for getting your boat into the water. Rather than sliding along wood and carpet, your boat slides along rollers for easier loading/unloading action.
Pros
  • Easier to get boat on/off trailer
  • Don't require deep submersion to launch boat
  • Distribute weight evenly, so less stress on trailer beams
  • Won't corrode as quickly
Cons
  • No friction - can lead to premature launch if winch strap removed too soon
  • Boat sits higher on trailer (greater center of gravity = more sway)
  • More moving parts require upkeep/more expensive to maintain
  • Cost more upfront
Boat Trailer with Rollers

Boat Trailer Legal FAQs

In some ways, buying a boat trailer is like buying a vehicle. It's fun and exciting, but it comes with some less fun paperwork to take care of. A few common questions we get about boat trailers:Do Boat Trailers Have Titles? Yes! Most US states require boat trailers to have titles. Check with the DMV in your state, but in general it's safe to assume you'll probably need a title.Do You Need Insurance for a Boat Trailer?Some states do require trailer insurance. Even in states in which it's not required, it's usually a good idea to have at least some level of coverage. Sometimes your current auto policy will extend to a trailer you are towing, but often separate coverage is needed to protect your trailer and its contents. Don't assume that your trailer is covered! Check with your insurance company to see what your current policy covers, whether a separate policy is needed, and what type of coverage is available.
Still have questions?Give our experts a call at 800-298-8924, or contact us online. We're happy to assist any way we can!
Amber S.
About the AuthorAs a content writer for etrailer, I might spend my morning loading and unloading a bike on five different bike racks to figure out which is easiest to use. I might be in the parking lot, taking pictures of an impressive RV battery setup our techs came across in the shop and discussing the benefits of the setup with the owner. I might spend an afternoon in a manufacturer training classes for some hands-on experience with new products, and then sit down to assemble all this information into a coherent article. At etrailer, one of our core values is that we are always learning, and I learn something new every day. I start each morning with the goal in mind of taking all of this information and figuring out the best way to answer the questions people ask us (and the ones they don’t know to ask yet), and helping people get the solutions they need to make their lives easier, safer, and more fun. I’m a DIYer at heart, so it brings me great joy to help a fellow DIYer find what they’re looking for, whether that’s a product, an answer, or a community.
Related ArticlesRelated ProductsWritten by: Amber S.Updated on: 5/22/20


Departments

Towing

Sports and Recreation

Trailer Parts

Vehicle

What our customers are saying:

"very easy to shop"

Mike
Richmond, CA

Popular Vehicles