When you’re a skipper accommodating groups of passengers regularly, it’s important to keep one specific element in mind at all times: the weight capacity of your vessel. The last thing you want to do when preparing your boat is possibly overload your craft. Not only is overloading a boat a classic rookie mistake, it can make your journey unsafe, not to mention inefficient. Boat literature would have you know that not overloading means not surpassing the weight capacity written out in the owner’s manual. Cut and dry, right?
Well, not so fast. In this article, we’ll show you exactly how to ensure you don’t overload your boat and cause a potentially dangerous situation for those onboard.
Above: A group of friends together for a sunset cruise birthday party onboard a sailboat. Photo by Maksim Goncharenok from Pexels.
Boat Capacity Plate: Know Your Vessel’s Limitations
The first thing you’re going to want to examine is the boat’s capacity plate. This capacity plate contains pertinent information regarding safe maximums for your boat. Normally, the following information is located on the plate:
- Maximum number of passengers
- Maximum weight of passengers
- Maximum combined weight of passengers, gear and motors
- Maximum horsepower motor the boat is rated for
As a general rule, these characteristics take into account the presence of fair weather. Additionally, the information on the capacity plate may change depending on the type of boat in question.
Capacity Plate Location
On practically all modern motor boats the capacity plate is in clear view from the helm controls, as required by law. However on some older boats (especially those built prior to August 1, 1973, when capacity plates became required by law) the placard can sometimes be back by the engine on the transom or near the stern.
All capacity plates should include the above stated specifications that indicate what your boat can legally carry. Some plates may contain a serial number along with the boat manufacturer’s name and the model number. The information you see on the capacity plate should also be contained in the boat’s owner’s manual for your convenience. Per federal law, single-hull motor boats that don’t surpass 20 feet must have a capacity plate. However, sailboats, kayaks, inflatables and canoes are not required to have this capacity plate.
It’s important that you follow the weight specifications on the capacity plate and other pertinent operating recommendations contained the owner’s manual. In most states, surpassing the specified maximum weight limit of your boat is illegal, although you may not get a ticket it is certainly not safe.
What Is the Importance of Your Boat’s Limits?
Depending on the type of boat you own, this is what your capacity plate might look like:
Outboard Motor Specifications: When boats have outboard motors, the plates specify that the maximum passenger limit in pounds and/or persons, maximum weight capacity of people, motor, and gear in pounds, and maximum horsepower.
Inboard and Stern Drive Powered Boats: These capacity plates will state the maximum Passenger capacity in pounds and/or persons, plus the max weight capacity of persons and gear in pounds.
Manually Propelled Boats: Manually propelled boats contain the same information as the previous categories.
Behind Capacity Definitions
So, you know now the categories but what exactly do they mean and how are the calculated? Let’s take a closer look at how these limitations are factored for your boat. The following is how the info found on the capacity plates is actually defined:
Maximum Passengers: This is the highest number of adults that a craft may carry without increased levels of danger. Normally, manufacturers assume that an adult weighs about 150 pounds when they formulate these numbers.
Maximum Weight (Or Gross Load): This number includes the total combined weight of all passengers on board the boat. This number can be more useful than the passenger number limit because it only factors in raw weight of passengers and load aboard the boat. If the 150-pound average is off, this figure will allow you to determine how many people should board the boat more efficiently based on what is actually onboard.
Persons, motor, gear: This number is the maximum weight of everything on board. The people, the equipment and the gear are added to reach this number.
Maximum Horsepower (HP): This displays the maximum horsepower that your boat transom and hull are constructed to support, under load, underway. It’s not wise to overpower your boat for a number of reasons. Among those are weight, where if an engine weighs too much it may cause your boat to sit too low in the water, allowing water to come over the transom or gunnels and swamp scuppers and drains. Beyond this, overpowered boats can cause stress fractures, gelcoat cracks, fiberglass damage and even structurual failure of the hull. Boats with more power than intended can also be extremely difficult and dangerous to control.
There is a special certification known as the National Marine Manufacturers Association, including capacity plates with much more info. This information will include inspection of lights, the efficiency of maneuvering, and more.
What If Your Boat Doesn’t Have A Capacity Plate?
If your boat doesn’t have a capacity plate, there is a simple formula you can use to calculate the maximum capacity of the vessel to ensure you don’t overload the boat. Fortunately this is fairly simple to do manually.
Below is the basic formula for calculating a vessel’s capacity:
The number of maximum passengers should be roughly equal to the boat’s length, multiplied by the width, divided by 15. The boat’s length and width should both be measured in feet for this formula.
Take the following example into account: Let’s say you have a 30 foot long boat with a 10-foot beam (width). First, multiply the 30 by the 10. The result is 300 square feet. Divide 300 by 15, which is 20. If you don’t get an even number, you can round up or down to the nearest integer. In this case, you could likely safely accommodate 20 adults.
Remember, this formula already assumes that the average adult weighs 150 pounds. If your passengers are a bit on the heavier side, you will need to reduce the number of people on your boat accordingly, and if you have more children, you can adjust the other way.
Many skippers recommend adjusting the number used to divide the boat, depending on the water conditions. When the water is calm, you may use 14 to divide instead of 15. If you’re estimating a faster speed on average, or if you have the wind at your back, you could bump the number to 16 or 17.
Coming up with the passenger capacity will not give you laser-sharp results. Take a peek at your manual to find out the most accurate specifications. You should only use the capacity formula if you need to determine these figures in a pinch. It’s never a bad idea to go back and do the math again using more precise figures based on the manual.
What’s the Best Way to Avoid Overloading Your Boat?
A few simple capacity rules will help you avoid placing too many guests on your craft. Use the following tips to avoid bogging down your boat.
- Follow Max Weight Protocol
The most simple way is by staying below the capacity printed on the plate. This is pretty cut and dry, but remember, when you have a smaller craft with a lower capacity, you’ll need to be very selective about what you bring with you on board. If you’ve heard reports of possible bad weather, you may want to stay light and shoot below the capacity just to be safe. - Don’t Pick Up Additional Passengers
You should never take additional unplanned passengers during your trip. Stick to your float plan and the information on the plate that you’ve reviewed. If it’s not available, use your manual. In the worst-case scenario, use the formula you learned in this article. However, keep in mind this is the LEAST ACCURATE calculation. - Even Weight Distribution
Distributing the weight equally throughout the vessel is required to avoid any leaning, listing or rolling during your trip. Leaning can cause significant problems, including stress on your boat, a sick group of passengers, and you may end up throwing your gear into the water. Trim tabs can help here, but it’s best to get the weight distribution right, and only make minor adjustments with trim tabs. Manufacturers go through several steps to do most of the balancing for you. This is why the seating and cargo storage areas are arranged in a strategic manner. When elements like the weather and passengers and gear exiting and entering the boat come into play, the lean balance in your craft will also begin to shift. - Avoid Heavy Weight In Inclement Weather
The figures on the capacity plate apply to fair weather (remember from earlier). When the water contains moderate chop, you should keep the load as light as possible. During the chance of higher waves, a heavy boat can be extremely difficult to maintain control over. Heavy gear will cause quick changes in the weight distribution as well. This will make controlling the craft unpredictable. This is why it’s critical to plan ahead and keep the weather at the forefront of your trip plans. - Don’t Overpower The Boat
Engine power has nothing to do with the weight and passenger capacity; it’s important that you understand the information regarding horsepower since it’s listed on the capacity plate. This means the limits are contained on the plate for a reason. They shouldn’t be ignored. Remember, when you want to fish you should buy a fishing boat. If you want to tow things, you should buy a tugboat. What should you buy when you want to drive a boat at high speeds? That’s exactly right, a speedboat. Stick to what your boat is efficient at doing, and don’t max it out beyond its design capabilities. Stick to the standards contained on the capacity plate and always remain mindful of the weather. Remembering these tips should lead to a safe and relaxing day on the water.
Frequently Asked Questions
What can happen if I overload the boat?
When you overload the boat, several things can happen. At a minimum, your boat will be more difficult to control, and you’ll have issues with leaning. Equipment may fall overboard and your boat may flood (swamp) or possibly capsize in the most severe cases. It’s also possible to receive a citation if marine officers find out your boat is overcapacity.
Where can I find the capacity plate?
As stated above, this is normally located beside the helm or within view of the main control station. Alternatively it could be near the transom around the stern of the vessel.
Do children count the same as adults on a boat?
No. Children are counted as one-half of an adult. So, for each adult you can carry, you’ll be able to carry two children.
Written by: