Knowing how much the maximum horsepower is allowed on your boat is an essential piece of safety information. Without this detail you run the risk of overloading your boat with an engine too powerful, which can lead to sinking and over-power. But where can you find the maximum horsepower for your boat? The quick answer is below, followed by more detail.
You can find the maximum horsepower for your boat on the capacity plate. Federal law requires any boat over 20 feet in length has a capacity plate installed by the manufacturer which lists the maximum number of passengers you can carry, maximum gross load, and the maximum horsepower allowed.
What does a boat capacity plate look like?
The boat’s capacity plate will list the maximum horsepower for your boat and can usually be found located near to the helm, steering area, and in full view of the captain.
This what a capacity plate looks like (image credit boaterexam.com) and where you can find it on a typical boat.
Did You Know? Small personal watercraft like kayaks, inflatable pontoon boats, and anything less than 20 feet in length are not required by federal law to have a capacity plate.
What does a horsepower rating mean on outboard boats?
Despite what you might think, the horsepower rating on an outboard boat has nothing to do with the speed you can drive it at. This is a common misconception, and one which I want you to pay attention to, as it’s very important.
The horsepower rating concerns the engine weight and is listed on the capacity plate as a safety signal to the owner to not install a heavier engine.
If you do put a higher spec engine in the boat with more horsepower, and thus more weight, it can put the flotation calculations out of sync.
If you do opt for more HP than that listed on the capacity plate it means your boat could sink if it gets swamped.
If you don’t exceed the horsepower rating, you have the peace of mind in knowing that should it capsize, it won’t sink, and passengers can hold onto the sides until they are rescued.
How much HP does my boat need?
For a very rough guide on how much horsepower your boat will need you will need to first know how much your boat weighs.
The general rule of thumb is to then have one horsepower for every forty pounds in weight of your boat.
As a real-world example, let’s say you have a 5,000-pound boat you would divide 5,000 by 40. That then gives you 125 horsepower – simple!
How is boat load capacity calculated?
When the boat is manufactured it will be designed and built to strict safety guidelines. Part of that process will involve calculating how much load the boat can carry, including the weight of the engine (relating to horsepower).
Before you consider calculating the boat load capacity yourself, please do check for the capacity sticker. It will usually be in view of the captain’s helm – you can buy a replacement if yours is missing.
The capacity plate will have the official boat load capacity and maximum horsepower listed on it.
However, if you have lost yours and want to understand how boat load capacity is calculated, here’s a very rough guide.
Length of boat x width of boat / 15 = number of passengers the boat can carry
In a real-world example, let’s say your boat was 20 foot long and 10 feet wide, the capacity would then be 20 x 10 divided by 15, which equals a load capacity of 13 passengers.
Now you know how many passengers your boat can roughly hold, you can then put a weight figure onto the number, giving you the load capacity in pounds.
The average weight of a person is 150 pounds.
Number of passengers x 150 pounds = boat load capacity
In the example above you would take the 13 passengers and multiply that by 150 pounds, giving you a load capacity of 1,950 pounds overall
You can see an actual calculator that I developed for pontoon boat owners which helps you come up with a rough guide to load capacity limits: pontoon boat weight calculator.
Handy Hint: The calculation above is only intended for vessels which are shorter than 25 feet in length. Please be aware, it is for illustrative purposes only and should only be used as a rough estimate and should not replace your manufacturer’s guidelines.
You might also like…
If you are interested in boat horsepower topics, you can read much more on the Pontoonopedia website. I’ve linked a few of the more popular articles below for you to browse through.
- 32 examples of the maximum horsepower on pontoon boats
- What does horsepower rating on a capacity plate mean?
The last word…
And there you have it; that’s where you can find the maximum horsepower for your boat. For more advice, hints, and tips please explore Pontoonopedia. If you like what you see, please share on social media!
