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Take The Hassles Out Of Trailering

Boat trailers require some maintenance to keep them rolling, or you could find yourself on the side of the road.

Two pickup trucks each towing a boat behind them cruising down a highway.


Pity the poor trailer. While its precious cargo gets all the attention, the trailer is likely to spend day after day neglected in the corner of a storage lot or at home. If the boat so much as coughs, the owner drags out his tool kit. But the only tool that comes anywhere near many trailers is a lawnmower.

To be fair, trailers are pretty simple, and there are only a handful of moving parts: a few rollers, wheels, and brakes, along with a bare-bones electrical system. But trailers do require at least some maintenance to keep them rolling, or you could find yourself at the side of the road. The proof is in the large number of calls each year that are received by the BoatUS TRAILER ASSIST® program. We'll examine typical calls for on-road assistance to see why members' trailers broke down and how the breakdowns could have been prevented. A little maintenance before the start of a trip sure beats the misery of a breakdown on a sweltering August afternoon.


Almost half — 44 percent — of all calls for assistance were for flat tires. Unlike automobile tires, which typically are used every day and lose tread gradually, trailers tend to be used infrequently. While the tread may look healthy, looks can be deceiving. Instead of failing after tens of thousands of miles of hard driving, trailer tires tend to fail after many years of sitting quietly. Sunlight degrades and weakens the sidewalls.

A large boat tips over into the road, apparently fell off the trailer it was on. A man steps out of his black SUV to look at the boat.

When a flat tire alerted this owner to worn tires, he promptly treated his trailer to four new radial tires. But radials have softer sidewalls and can cause a trailer to sway more than the driver might be used to. Once this trailer started swaying, it didn't stop until the boat was thrown from the trailer, breaking the tie-down straps.

Before the start of any trip, look for spider-web cracking on the sidewalls, which indicate the tire has rotted and must be replaced. Removing the tires and bringing them inside (set blocks under the axles) when they won't be used for a while will prolong their life (and will also help to deter theft). If you can't store your tires, cover them with a tarp.

Is Parking On Grass Bad For Tires?

For years, consumers have been reading that parking their trailer on grass can rot the tires. A quick online search brings up pages of the same thing. But Doug Grassian, Director of Consumer Communication for Goodyear Tires, says that's a myth. "Modern rubber compounds aren't affected by sitting in wet grass," he said. "It's OK to park on the grass, but the best place to park a trailer is on gravel or a hard surface like concrete or asphalt." Grassian says while your tires may be OK on grass, metal components of the trailer may corrode faster if they're exposed to the moisture of your backyard.

Trailer tires that sit for long periods suffer from another problem: under-inflation. Tires lose about a pound of pressure per month and another pound for every 10 degrees the temperature drops. An underinflated tire is more likely to fail and could also cause the trailer to fishtail, or sway. When a trailer has been sitting for many months, step one before starting a trip should always be to check inflation.

Even if you take exceptional care of your tires, road debris could someday cause a flat. Do you have a spare? Do you have a jack? (A typical car jack will not work on a trailer; you'll need a scissor jack or a hydraulic jack that is big enough to handle the load.) Do you have a properly sized lug wrench? Will the lug nuts be rusted onto the wheel?

Even with the assistance of TRAILER ASSIST, the quickest way to get back on the road is to carry a spare. Leaving your trailer by the side of the road, even for a while, runs the risk that gear, the motor, and/or the trailer could be gone when you return. And, unlike a damaged automobile tire, finding a replacement for a damaged trailer tire can sometimes be difficult. For more on what you need to have with you when you trailer your boat, see "Boat Trailer Toolkit".

Keeping Your Bearings

Twenty-one percent of the service calls to TRAILER ASSIST are for bearings. If your hubs don't have bearing protectors (metal caps with springs that hold grease under pressure), it is best to keep them out of the water. If the hubs must be dunked, allow time for them to cool, or cold water will be drawn inside, displacing the grease and causing the bearings to corrode and fail.

Dry trailer bearing

This bearing failed on the highway because of lack of maintenance. A bearing with dried out grease won't get your boat safely to the launch ramp — or back home.

Bearings that have been accidentally submerged in saltwater should be cleaned before being repacked with grease. Use something like a tongue depressor to distribute the new grease evenly to both front and rear bearings (don't overpack). With most hubs, seals must be replaced whenever they're removed for packing. Most new trailers, fortunately, come with bearing protectors, which eliminate water penetration into the hub, not to mention a lot of grubby work.

If your trailer doesn't have protectors, they can — and should — be added to the hub. They're easy to install and are relatively inexpensive.

With protectors, a squirt or two of grease at a fitting is all that is required to safeguard bearings. Press the protector at the edge. If it moves it doesn't need grease. If it is rigid, you'll need to add grease (use only a grease recommended for trailer bearings). Even with protectors, boat owners who trailer long distances should carry a hub kit that has everything needed to replace bearings on the road. They're available for about $50 to $60 set.

Axles And Frames

There is nothing complicated about a trailer frame and axle. Bolted to the trailer suspension, with a tire at each end, there's not much to go wrong.

Question: So why are 10 percent of the service calls for axles?

Answer: Rust!

A rusty axel boat part

This axle is so badly rusted it finally broke, stranding the owner on the side of the road.

Submersible trailers have the advantage of being easier to use, at least for beginners, but they have the disadvantage of requiring more upkeep, especially when the trailer is used in saltwater. If you do a lot of trailering, consider buying an aluminum trailer. Aluminum costs more than steel but is less susceptible to corrosion.

Axles are usually held in place with U-bolts, which are prone to rusting, and the axles themselves, which if dunked and ignored, can be weakened by rust. Any light rust on the trailer's frame should be sanded and painted. The sooner the better.

If an axle or structural component appears to be badly rusted, the trailer shouldn't be used until it is examined by an expert or the component has been replaced. Rust often starts inside the frame, so surface rust may be more serious than it appears. To prevent rust, any trailer, even those with a galvanized frame should be rinsed thoroughly when the trailer has been dunked in saltwater.

Trailers tend to get bounced around a lot, and any loose nuts on the frame must be tightened. If you aren't familiar with your trailer, structural components should be inspected frequently until you're confident that none are prone to loosening. Even the tightest trailer should be examined routinely on long trips.

Trailer Towing Tips

  • Make sure the trailer can handle the weight of the boat and gear. The gross vehicle weight rating (GVWR) is marked on the trailer. The load should be no more than 85 percent of the rating.
  • Be sure your tow vehicle can handle the combined weight of the boat, trailer, vehicle, and gear — referred to as the vehicle's gross combined weight rating, or GCWR.
  • The trailer hitch must be within the limits of the tow. Make sure the hitch is the proper class rating.
  • Ensure that the tongue weight on the hitch is 5 to 10 percent of the total load. Too little weight will make the trailer prone to fishtailing, one of the main reasons for serious towing accidents. (Fishtailing can also be caused by underinflated tires or because the trailer and boat are too heavy for the vehicle.) Conversely, too much weight on the hitch will make it difficult to steer the vehicle.
  • Secure the coupler with a pin or lock so it doesn't come off of the hitch ball — if the ball and coupler are matched. A 2-inch ball won't stay on a 1 7/8-inch coupler for long. Don't forget to cross and fasten the safety chains to the vehicle's tow hitch.
  • Keep up with maintenance on the trailer's bearings. Stop frequently to check that the hubs are not overheating. Overgreasing hubs can cause the grease to ooze out and migrate to the brakes.
  • The proper tires, frequently inspected for cracking and properly inflated, will prevent the most common of all trailering breakdowns — flat tires. Slower speeds generate less heat and extend tire life. Remove or cover tires when not in use.
  • Corrosion is the biggest killer of trailers. Inspect the axles, springs, and connecting hardware frequently. Wash down the trailer any time it's been dunked in seawater.
  • Check trailer lighting before every trip. While conventional lights are prone to failure, LED trailer lights are shock- and waterproof and will likely outlast your trailer. Tie downs are a must for all boats, even for heavy ones that you think can't get away — they do.
  • Ensure the proper operation of brakes, if equipped. Surge brakes must be adjusted periodically. You'll have to jack the wheel off of the ground and then use a brake tool to first tighten the adjustment cog all the way until the wheel won't turn and then back it off until the wheel again turns freely. If you do the job yourself, follow manufacturer's recommendations.
  • Make sure the breakaway cable is functioning.

Sample Of Trailer Claims And How They Could Have Been Avoided

Claim: "Driver tried to stop on rain-slick road and weight of trailer pushed [the truck] into a ditch. Boat landed in back of truck."

Prevention: Slow down! The weight of your boat makes your vehicle handle differently, which might not be apparent until a sudden maneuver is needed. And rain makes everything a little dicier.

Claim: "Rusted axle broke and boat came off of trailer and landed on roadway."

Prevention: Inspect axles and suspension regularly. Replace any parts that are badly rusted.

Claim: "Overloaded tire blew out and boat fell onto highway, backing up traffic for hours."

Prevention: Use ST-rated tires, don't exceed weight limits, and slow down! Slower speeds produce less heat, which prolongs the life of a tire.

Claim: "Trailer began fishtailing and broke away from the tow vehicle. The trailer and 28-foot boat are in a ditch."

Prevention: Only experienced drivers should tow large boats. Making sharp lane changes can start the boat swaying and send everything — car, boat, driver, and weekend plans — into the ditch. Also make sure the trailer is balanced; 5 to 10 percent of the total load should be on the hitch. An unbalanced trailer is prone to fishtailing.

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Charles Fort

Contributing Editor, BoatUS Magazine

Charles Fort is BoatUS Magazine's West Coast Editor. He often writes local news items for BoatUS Magazine's Waypoints column and contributes to Reports, in-depth tech features in every issue written to help readers avoid accidental damage to their boats. He is a member of the National Association of Marine Surveyors, he's on ABYC tech committees, and has a 100-ton U.S. Coast Guard license. He lives in California.