Trailers: (Almost) Everything You Need To Know About Hauling Your Boat Or PWC

Everything you should know about a boat or PWC trailer.

28th April 2010.
By Jeff Hemmel

Most of us dream about keeping a PWC or boat at our waterfront dock, but the reality for most of us is trailering, loading our prized possession onto a wheeled cart and towing it to the water. Another reality is that, while many of us can recite the spec list about our craft, we know little about the trailer. In the long run, that could be a big mistake.

So, I’ve put together some information, an “everything you wanted to know about boat and pwc trailers…but we’re afraid to ask” sort of thing. Here, in no particular order of importance, is what you might want to know about your trailer.

Size — It’s obvious a trailer should fit your boat. For trailerable boats (those under 8′ 6″ in beam, take into account two measurements — length and weight.

Length should be measured from the farthest point at the bow  to the end of the hull’s running surface. In general, trailers are typically about two feet longer than the boat itself. Do not use LOA (which can be influenced by extended swim platforms) as an indicator of boat length, as a trailer only supports the hull’s running surface.

Weight means more than just the manufacturer’s spec sheet claims. You need to know your craft’s wet weight, as it accounts for fuel (8.5 pounds per gallon), water (6.5 pounds per gallon), and other items like the batteries, gear, and add-ons brought aboard. Boats under 3500 pounds can typically be hauled with a single-axle trailer; those over 3500 pounds are best carried by a tandem-axle model.

Frame —The frame of a trailer gives it its structural integrity. Frames are typically made from steel or aluminum.

Tubular steel offers excellent strength, as well as protection for wiring and brake lines, which can be run inside the frame. Steel can also be painted to match the color of your boat or tow rig. Steel, however, can rust, a fact which will affect not only the look of your trailer, but also its structural integrity over time.

Steel is most commonly painted, and can be color matched to your boat for that custom look. Painting is also relatively inexpensive. It does, however, require more perioidic maintenance to keep looking fresh, as any metal that starts to rust will quickly affect the paint.

Paint can also chip, or dull over time. Galvanized trailers offer far superior corrosion resistance, but do not offer the potential for color. Metal is dipped into a bath of liquid zinc at 500degrees C, a process known as hot-dip galvanizing, and come out with a protective coating of silver-colored zinc. The finish offers a superior layer of protection, and is almost a must for saltwater boaters.

Aluminum trailers are made from aluminum I-beams, which offer a superior strength-to-weight ratio compared to steel, but offer less protection than tubular designs. Wiring and brake lines should be run in conduit and secured to the inside of the structure for protection.

Axles — Tandem axle designs are best for loads under 3500 pounds; above 3500, a tandem axle design is best.

Suspension — Wheels can be linked to the trailer frame by one of two primary suspension methods – leaf spring or torsion beam. The most traditional form of suspension, leaf springs consist of a series of curved, slender steel plates, placed atop each other, which flex to absorb shock. Torsion beam suspension uses a torsion bar as the weight-bearing spring. A soild metal bar is attached to the trailer frame; the opposite end featues a lever attached to the axle. Shock absorption is provided by the bar’s torsion resistance, typically rubber cords located inside the axle housing.

Hub Bearings — Hub bearings are typically protected by grease, packed inside the hub and forced into the bearings to prevent friction and heat build-up. An alternative system is oil bath lubrication, which uses a reservoir of oil to continually coat the bearings as the rotate.

Spring-loaded bearing protectors, like the Bearing Buddy, protect the bearings and keep grease contained, while allowing easy visual inspection of the grease level. Manufacturers claim the spring pressure also prevents water from entering the hub when submerged. A grease fitting allows more grease to be added without removing the hub.

Bunks vs. Rollers — Trailer bunks provide support along much of the entire length of the hull. Bunks are typically made from wood, covered in marine-grade carpet. Composite bunks are also available. Rollers typically provide easier loading and launching, particularly on gently sloped launch ramps, but often do not support the hull as well as a comparable bunk. Rollers may also dimple the hull. Check with your boat manufacturer, as they often suggest a certain type of trailer for best support.

Brakes — Laws vary by state, but typically brakes are required for all wheels on any trailer that grosses in excess of 3000 pounds. Hydraulic surge brakes are the most common trailer option in boating, partly because they are far more tolerant of water than their electric alternative. Hydraulic surge brakes are activated by the change in momentum caused by the tow vehicle as it decelerates. The trailer’s momentum pushes the brake housing forward, which ultimately forces brake fluid out of the master cylinder and into the wheel cylinders, activating the trailer brakes. Surge systems can be used with either drum, or disc-style brakes.

Drum brakes work by forcing a pair of brake shoes against the side of an enclosed drum. Drums feature more parts, are typically harder to service, yet are relatively inexpensive. They may also be better for lighter trailer loads, as they don’t require the higher pressure of disc brakes, and often have more surface area on the pads. Many brake experts contend drums are better whe the Gross Vehicle Weight (GVW) is under 3000 pounds. The primary disadvantage to drum brakes is that they contain water, possibly resulting in far faster corrosion and failure.

Disc brakes use hydraulic pressure to force a pair of brake pads to squeeze against a rotor, located behind the wheel hub. Discs are generally less complicated internally, require fewer adjustments, but more expensive up front. Disc brakes also feature no enclosed parts, making them far easier to rinse off at the end of the day with fresh water and less likely to suffer from rust and corrosion.

Trailers with drum brakes should have a hose connection to allow flushing the brake’s internal surfaces with fresh water. Essentially a system of tubing plumbed to a hose connection affixed to the trailer, a flush kit gets fresh water into areas that would normally be inaccesible to a hose, and greatly reduces the chance of rust and corrosion over time.

“Breakaway” Brake — Trailers requiring brakes must also be fitted with an emergency brake activation system in the event of a breakaway. On hydraulic systems, brakes are typically triggered by a small cable that runs from the trailer coupler to the tow vehicle’s hitch; this cable activates the brake’s master cylinder when pulled.

Winch — A trailer winch allows the boat to be pulled up onto the trailer with relatively little effort, and also serves as a tie-down point for the bow once the boat is in place. Typically winches are mechanical, requiring a handle to be cranked to wheel the strap or cable onto the winch barrel. Electrical winches are also available. Winches should only be used to pull the boat the last few inches into position, and not to pull a boat entirely out of the water.

The winch post should be adjustable on two planes; forward and back as well as up and down. Forward and back adjustment is essential to position the boat properly on the trailer and to achieve the required tongue weight. Up and down adjustment is necessary so that the winch post roller contacts the boat in the correct position for support, as well as to act as a stop when you drive the boat onto the trailer.

Safety Cable — Safety chain or cable is designed to run from the trailer tongue to the tow vehicle to prevent accident or injury in the unlikely event your trailer comes off the tow ball. Chains should be crisscrossed under the coupler, short enough to catch the tongue before it hits the pavement in the event of a failure, and feature beefy S hooks to secure to the cable attachments provided on the vehicle or hitch.

Tongue Weight — Tongue weight can be defined as the downward weight the trailer and its contents place upon the hitch ball. As a rule of thumb, tongue weight should not exceed 10% of the gross trailer weight, the weight of the trailer itself with the fully loaded boat in place. Too little tongue weight and the trailer will sway from side to side, or surge forward and backward. Too much tongue weight and the tow vehicle will suffer impaired handling, as well as excessive wear on the rear tires over time.

Tongue Jack — A tounge jack allows the tongue to be easily lifted and lowered on and off the hitch ball. Jacks typically feature a wheel at the base to allow the trailer to be moved about and positioned above the hitch ball. Jacks can also feature a solid foot pad to prevent the trailer from rolling.

Grommets — Look for rubber grommets anywhere wiring or brake lines pass inside or through the trailer frame. They’ll prevent the lines from being chafed or cut by the bare metal of the frame, preventing a troublesome short or loss of brake fluid.

Lights — LED lights are considered a vast improvement over low-tech, incandascent bulbs as they offer a far longer lifespan, can be sealed from water intrusion, use less energy, and are, on average, far brighter than incandescent bulbs.

Load Guides — Made from either PVC pipe or padded boards, load guides help position the boat properly on the trailer, will not mark the boat’s hull, and also serve as a visual reference of the trailer’s rear corners when backing an empty trailer down a launch ramp or into a parking space.

Load Index — Make sure your trailer tires are rated to carry the load of your fully loaded boat and trailer. Look at the tire’s Load Index, the last set of numbers following the tire’s size description. This number indicates the maximum weight a tire can support. Typically ranging from about 80 (a 992 pound load capacity) to 110 (2337 pounds), make sure the cumulative total exceeds that of your load. That letter that follows the load index? It’s the tire’s maxiumum speed capability, typically between an R-S (106-112 mph) on most trailer tires.


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About the author:

Jeff Hemmel

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Jeff Hemmel writes for boats.com, Boating, PersonalWatercraft.com, and Powersports Business. The former Senior Editor at Watercraft World, Jeff is a multi-time award winner as well as a 2008 inductee into the IJSBA Hall of Fame. His first book, "The Anti-Pirate Potato Cannon...and 101 Other Things For Young Mariners To Try, Do, & Build On the Water," received a bronze medal in the 2010 Moonbeam Children's Book Awards. For more info, visit Jeff Hemmel's website.

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