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Avoid Fishtailing And Jackknifing With A Boat Trailer

Fishtailing and jackknifing boat trailers are scary and can be dangerous. Here's what you need to know to help avoid these problems on the road and at the ramp.

Towing a boat along the highway

"I've gotta hit the brakes!"

Those were the last words I wanted to hear as the trailer carrying my 22-foot Sea Ray fishtailed on the hitch of the big sedan. At that moment, we were about to pass an oncoming car "port to port" on the two-lane bridge spanning the stream, so there was no room for error. As my friend Nat stood on the brakes of our tow vehicle, I watched in the passenger mirror as our heavy yellow hull cut drastically to the right and took out a telephone pole before spinning us around and stopping in a classic jackknife position in the middle of the rural two-lane road. We were facing the way we'd come, the still-connected boat and trailer balanced on the guardrail over a small creek, when a young, wild-eyed man knocked frantically on the driver's side window.

"Are you guys OK?!" he asked, continuing without waiting our answer. "I saw the whole thing and what you did! Are you OK?"

Nat and I just looked at each other and nodded our heads, breathing sighs of relief.

"I am so sorry, man, but I had to," Nat apologized to me. "That car was coming at us, and the way we were fishtailing I worried we'd pass 'em at the bridge and knock them off," he said, reliving the flash of events that led to our jackknifed rig. I acknowledged that he had done exactly the right thing in that circumstance and thanked him for having the presence of mind to do so. It turned out the other car also held the man's wife and two kids, and who knows what might have happened had Nat not assessed the scene, gone against his better judgment to keep his foot off the brake to let the fishtailing trailer come back into line, and done the polar opposite.

Bigger Is Better

When backing, a short trailer becomes more responsive than a long one, which makes it quicker in terms of angle mistakes. Most find it much easier to back a long dual-axle boat trailer than a short single-axle trailer designed for towing PWCs.

Two decades of towing boats had taught him a thing or two, which, along with the big V8 sedan he used as a tow vehicle, is why I asked Nat if he would help me trailer the 5,000-pound rig. He knew that the last thing you want to do when towing a trailer that has begun to "fishtail," or swerve side to side, is hit the brakes. When he uttered his fateful words, we both knew we were in for a ride and barely had time to brace for the event.

Back a Boat Trailer Like a Pro

Jackknifing At The Ramp

Jackknife at the ramp illustration

Our emergency on-the-road incident resulted in our rig's classic jackknife in mere seconds. While this happened as we were towing, many trailer-boaters arrive at the awkward position in a slow-motion process involving a series of missteps while in reverse at the launch ramp.

Backing a trailer is counterintuitive. To make the trailer move to the left, you turn the steering wheel to the right, and vice-versa. That's due to the ball-and-socket joint connecting the tow vehicle at the hitch. When driving forward, this articulated joint comes in handy, allowing your rig to turn and maneuver through traffic without requiring multiple lanes. That all changes when you back up, often resulting in the trailer and tow vehicle ending up at an acute angle to each other — resembling the folding blades on a partially opened jackknife.

Volumes have been written about how to back a trailer, including tactics, tricks, visual telltales, and high-tech aids and accessories such as video cameras and lane alert systems. Some late-model vehicles intended for towing even come equipped with automatic trailer-backing modes.

My best advice is to line-up the tow vehicle and trailer in front of where you want to back it, place your steering hand palm down on the 6 o'clock position at the bottom of the wheel, and as you slowly back-up, use that hand to turn the wheel in the direction you want the trailer to go. If a turn is called for, when your trailer reaches the angle you need to negotiate it, begin gradually correcting using the hand at the bottom of the wheel until the trailer is where you want it. Having a trusted "spotter" on the ground to guide you through the backing paces, verbally and with hand signals, can be a huge help.

Of course, sometimes you can't position the tow vehicle and trailer in front of where you want to back it, and the trailer must go into a slot that is at an angle to "straight behind." This requires practice, considerably more skill, and a lot of patience. "Baby steps" help. As at other times, having a spotter also helps. Anytime your trailer and/or boat come too close to impacting the tow vehicle or turning at right angles to that vehicle, slowly pull forward until the tow vehicle and trailer are aligned again, rethink what you're doing, and start over. Don't wait until it's too late. It's possible in extreme jackknife situations for trailers to end up in such a sharp angle to the tow vehicle that, as you pull forward to recover, the trailer follows not by straightening out, but by dragging its wheels sideways.

Jackknife on the road illustration

It's easier read than done. Like docking a boat, nothing replaces practice when learning how to back a boat trailer. And that's best done at a time and place where there is no pressure to perform. Take your time.

Jackknifing On The Road And Fishtailing

As for on-the-road jackknife avoidance, most situations are precipitated by trailer sway, or fishtailing. Trailer sway occurs when improper weight distribution, wind, humps, bumps in the road, or a combination of those factors, causes the trailer to get out of alignment with the tow vehicle and move back and forth. It's a classic case of the tail wagging the dog and can be terrifying at towing speeds.

That was the case at the opening of this article when towing the trailered boat slightly downhill and over the humped apron of an intersecting driveway created just enough of a lift to cause the trailer's wheels to reduce contact with the pavement and set the trailer into fishtail mode. Normally, trailer sway can be eliminated by taking the foot off the accelerator and allowing the rig to slow down until the trailer gets realigned. The opposite can also work: speeding up can realign the trailer, but it's a gutsy move that calls for the right circumstances (level road, little traffic) to attempt. The last thing you want to do in a fishtail situation is to brake hard, which will cause the momentum of the trailer to push the back of the tow vehicle, reducing its contact with the road surface. In turn, this threatens putting the rig into the classic jackknife position Nat and I experienced.

With some rigs, brake controllers and anti-sway devices may be helpful when towing, but this is beyond the scope of this article.

Weight Matters

Improper weight distribution alone can cause a boat trailer to fishtail. One of the most effective ways to guard against fishtailing is to ensure that the weight load on your trailer is properly distributed, allowing 5% to 7% of the total weight of your loaded trailer felt at the trailer coupling ball when the tongue is parallel to the ground. A bathroom scale can be used to determine same. For example, if the gross weight of a trailer, boat, fuel and gear is 2,000 lbs., the weight on the tongue should not be more than 140 pounds or

Trailer tongue weight

You can easily establish your trailer's tongue weight using a bathroom scale.

If the weight on the coupling ball doesn't fall within the proper range, you should take steps to achieve it. If a small adjustment is called for, you may be able to attain the proper balance by shifting some of the gear in your boat — portable gas tanks, fishing or ground tackle, or ice-filled coolers — from back to front or vice versa. A more permanent fix is to adjust the position of the winch stand on the tongue, moving it forward or backward to support the boat in a different position atop the trailer.

The bottom line is, trailer sway and jackknifing are avoidable perils for those of us who tow, tow, tow our boats. In most cases, the operative word is to take it S-L-O-W until your ducks are in a row before you try, try again.

Retrieving Tips

One problem boaters can face when backing an empty trailer down a launch ramp to retrieve a boat is visibility — being able to see the trailer in the rearview mirror or window to monitor its angle in relation to the vehicle as it descends the slope and drops out of view. I carry a pair of commercial telltales designed for such instances. With a bright yellow plastic ball on one end of a telescoping metal rod that resembles automobile antennae, and a magnetic base at the other, I extend the rod, place one telltale on each metal fender or trailer frame corner, and use the elevated balls as visual references as I back down the ramp. Another trick I employ when backing an empty trailer with my pickup is so drop the tailgate to give me a lower sight window during the process. Caution is called for, however: A dent in the top of my tailgate serves as a reminder that you have much less room for angle error with the tailgate extended from the back of the truck in relation to the winch stand.

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Dan Armitage

Contributing Editor, BoatUS Magazine

A full-time travel and outdoors writer based in Ohio, Dan is in his 20th season hosting the popular syndicated radio show Buckeye Sportsman. He gets around on a pontoon boat and an Aquasport center-console, which he uses for all his DIY editorial projects and fishing features. A USCG Captain (Master 50-ton), he’s a popular speaker at boat and sport shows.