3 Ways To Figure Tongue WeightBy BoatUS Trailering Editors
Tongue weight is exactly what it says: the weight of the trailer tongue on the hitch of the tow vehicle. The rule of thumb is that you want a tongue weight equal to 7-12 percent of the total weight of the (fully loaded with fuel and gear) boat/ motor/trailer combo. Tandem- and tri-axle boat trailers usually require a percent or two less tongue weight than recommended for a single-axle boat trailer.
If the tongue weight is too low, the boat trailer will sway from side to side when you reach speeds of around 30 mph. If it’s too high, the trailer will “push” the tow vehicle, making it more difficult to control when braking because so much weight is on the tongue. It is important to have the trailer as By BoatU.S. Trailering Editors level as possible when attached to the tow vehicle. Too great an angle can affect the trailer’s braking ability.
To measure tongue weight, take the boat, trailer, and tow vehicle fully loaded to a truck scale or a landfill/recycling facility and use one of the following methods. Call ahead and see if they can accommodate you.
- Pull the truck onto the scale, leaving the trailer hooked up to it, but keeping the wheels of the trailer off the scale. Get the weight – let’s say it’s 4,600 pounds. Then drive off the scale, disconnect the trailer, and drive the truck back on the scale again and weigh it alone – let’s say the truck weighs 4,200 pounds. The difference (4,600- 4,200=400) is the tongue weight.
- Drive the truck onto the scale as in step 1, but instead, disconnect the trailer, leaving just the tongue jack on the scale, but the wheels of the trailer off the scale. Drive the truck off the scale. Get a 4x4 piece of lumber about 17 inches long, place it under the coupler where the ball would normally go, slowly crank the tongue jack until the tongue jack wheel is 1/4-inch off the ground, so the trailer is sitting only on the 4x4 (but don’t remove or swing the tongue jack out of the way in case the trailer falls off the 4x4). Read the scale. That’s your tongue weight weighed right at the coupler, where it should be measured. If you simply use the tongue jack as the weighing point, it skews the tongue weight to the heavy side.
- A quick way to check tongue weight is to use the Seasence 800 Tongue Weight Indicator Jack. It has a built-in scale and will provide a quick read of the tongue weight on the hitch. Note: The “800” designates the jack will measure up to 800 pounds of tongue weight. There’s also a 1,500-pound version.
TONGUE WEIGHT and a bathroom scale? Go to www.Boatus.com/trailerclub/magazine
How To Fix Improper Tongue Weight
- If the tongue weight is too low, the trailer axle can be moved back a little, or the boat can be moved forward a little. Sometimes, shifting a full ice chest or some full portable gasoline cans is enough to add the necessary weight to the trailer tongue.
- If the tongue weight is too high, more weight has to be moved off the trailer tongue. If heavy portable fuel tanks/equipment/ice chests are stored near the bow, the first step is to move them toward the rear of the boat – or into the tow vehicle. Many times this is enough to get a tongue weight that will work. This can also be done by moving a trailer axle forward – but not every trailer is designed for this to be done – or adjusting the winch post to a point farther back so the boat can be moved away from the tow vehicle. Any adjustment made for tongue weight has to be done in small increments.