Just like cars can only seat so many people, boats have operational limits as well. Most boats have a capacity plate that lists the maximum number of people, weight including gear and engine and the horsepower capacity for the engine. These limits should be followed at all times because they can lead to safety risks and fines if ignored.
Boats have have weight limits because if there is too much weight on board, the boat can be overstressed, especially in even moderately rough conditions. Too many people onboard can cause the boat to swamp and even capsize.
Tip: The weight and number of people must both be considered. If the maximum number of persons if 8, it is important to remember that 8 small children is different from 8 adults.
It is also important to remember that the capacity plate also has limits for the weight of gear as well, including the engine(s). If you are planning on doing a long trip with a lot of gear, make sure you are not exceeding the weight limit.
Finally, if you ever need to purchase a new engine for your boat, make sure the horsepower of the engine does not exceed the maximum horsepower for the boat. Overpowering a boat is a serious safety hazard because it could over-stress the hull and cause the boat to go faster than it is intended to.