An often overlooked aspect of safe boat trailering is the tongue weight of the trailer. First of all, what is “tongue weight”? Tongue weight is the force that the tongue of the trailer (thru the coupler) exerts on the hitch ball of the tow vehicle. Why is it important to know the tongue weight of your trailer before hitting the road? Well too little tongue weight can lead to an out of control swaying condition wherein the tow vehicle and trailer can leave the roadway, overturn, or come into contact with other vehicles on the road. On the other hand, too much tongue weight can lead to poor steering and braking performance of the tow vehicle which again, can cause a potentially fatal accident. So as you can see, tongue weight is something that should be measured and considered before you tow your trailer. One other point to mention prior to delving into the actual measurement and correction process is the towing “attitude” of the trailer. By this I mean the angle of the trailer frame relative to flat ground. Trailers are designed such that while in tow, the main frame rails of the trailer are parallel to the ground. So the first step in trailering is to assure that the proper tow vehicle, hitch, and ball mount are selected, not only in terms of their weight carrying capacity, which is critical, but also in terms of the attitude that it places the trailer in when connected to the tow vehicle. Again, we are shooting for as close to a level condition as possible. All other discussion from here on out will assume that all of the above has been taken care of.

What is the ideal tongue weight and how do I measure it?

Most experts agree that the ideal tongue weight for typical applications falls in the range of 9 – 15% of the gross weight of the entire trailer, including whatever loads are placed on the trailer at that time. We will refer to this as the “safe range”. Obviously one component of this calculation is the gross weight of the loaded trailer. If you have purchased a new boat and trailer combination, your dealer will often have a good estimate as to the weight of the entire rig. You then must consider the additional loads that you have placed in the boat such as: additional batteries, trolling motor, tools, fishing tackle, chain and anchors, ice, drinks, water, fuel, stereo equipment, T-Top or Bimini Top, electronics, etc. If you don’t already know the weight of your boat and trailer combination, you will need to carefully tow your rig to a truck stop or other facility that has scales capable of parking your trailer on and where you can unhook the trailer from the tow vehicle while the weight is measured. Now that you know your gross trailer weight, the final step is to measure the tongue weight of the trailer. There are at least a couple of possibilities here and these depend on the weights involved. If the trailer has an expected tongue weight of less than 300 lbs, you may be able to use a typical bathroom type scale to measure the tongue weight by placing the wheel of your trailer jack on the center of the scale and adjusting the height of the jack to reach a level attitude of the trailer’s frame rails. At that point, an adequate approximation of the tongue weight can be read directly from the scale. If the expected tongue weight is in excess of 300 lbs, your options are much more limited without access to some type of heavy duty scale or load cell arrangement. In this case, the TrailerSense Jacks from SeaSense are your best option. The 800 lb version is perfect for most standard duty applications. The 1500 lb version is made for heavy duty applications where tongue weights exceed 800 lbs. Both designs function the same. By releasing the built-in locking collar and supporting the weight of the trailer tongue with the jack only, then adjusting the trailer to the proper towing attitude (level), the tongue weight can easily be read from the scale on the side of the main support tube of the jack. Now, with these two important pieces of data, you simply divide the tongue weight by the gross loaded trailer weight to reach your percentage of tongue to gross weight. If this percentage falls into the safe range, you are ready to hit the road.

So if I find that my trailer’s tongue to gross weight percentage falls outside of the safe range, how can I adjust my tongue weight?

The magnitude of the problem should be considered first. If your tongue weight percentage falls right on or just outside of the safe range, there are often moveable items within the vessel that can be relocated forward or rearward, depending obviously on which end of the range you fall out of. You may also be able to load the boat just a bit farther onto the trailer to increase tongue weight or not load on quite as far to reduce tongue weight. If your tongue weight is typically fine, but suddenly you find that it is lower than normal, you should check to see that the bilge of the boat is not full of water. If you have checked everything, including your calculations, twice and your percentage falls well outside of the safe range, say by a couple percentage points, then you may need to make some significant adjustments to the trailer itself. If the tongue weight is too little, you may need to make adjustments to the bunks, bow stand, etc. that place the boat further forward on the trailer during towing. If the tongue weight is too high, the opposite may need to be done if possible. If the above are not options, the axle(s) may need to be moved forward in the case of too much tongue weight or back in the case of too little tongue weight.