People, maximum horsepower and weight capacity
A rule of thumb from the Coast Guard’s boater’s guide for boats without a capacity plate. It doesn’t account for the hull’s displacement and assumes 150-lb people.
Your boat’s capacity plate always overrides these estimates. The federal capacity formulas cover monohull boats under 20 feet, except sailboats, canoes, kayaks and inflatable boats; a pontoon boat is not a monohull.
What does a capacity plate indicate? The U.S. Coast Guard capacity plate shows the maximum number of people a boat may carry, as a number and in pounds, the maximum total weight of persons, motor and gear (persons and gear on an inboard or sterndrive boat) and, on an outboard boat, the maximum horsepower. Where can you find the maximum horsepower for your boat? On that plate, which must be where the operator can clearly see it when getting underway. Federal rules require the plate on monohull boats less than 20 feet long, except sailboats, canoes, kayaks and inflatable boats. For a boat without one, the calculator above estimates the people capacity with the Coast Guard’s rule of thumb and the maximum horsepower and weight capacity with the formulas in 33 CFR 183.
The capacity plate always overrides an estimate. The federal formulas apply to monohull boats under 20 feet, except sailboats, canoes, kayaks and inflatable boats. A pontoon boat is not a monohull, and boats 20 feet or longer are outside these rules: use the builder’s figures for them.
What Does a Capacity Plate Indicate?
| Boat | Lines on the plate |
|---|---|
| Outboard | Maximum persons (number or pounds); maximum pounds of persons, motor and gear; maximum horsepower, on some boats one figure with remote steering and one without |
| Inboard or sterndrive | Maximum persons (number or pounds); maximum pounds of persons and gear |
| Rated for motors of 2 hp or less | Maximum persons (number or pounds); maximum pounds of persons, motor and gear; maximum horsepower |
| Oars or paddles | Maximum persons (number or pounds); maximum pounds of persons and gear; This Boat Not Rated for Propulsion by Motor |
The capacities appear under the heading U.S. Coast Guard Maximum Capacities on a yellow panel. The rule (33 CFR 183.25) puts the plate where the operator can clearly see it when getting underway, and the BoatUS Foundation says plates are generally on the inside of the transom or next to the helm. BoatUS also points out that the limits apply in good to moderate weather, and that the number of seats is not an indication of how many people a boat can carry.
Where Can You Find the Maximum Horsepower for Your Boat?
On an outboard boat with a capacity plate, the horsepower line is the maximum: never exceed it. If your boat has no plate, ask the builder; for an outboard monohull under 20 feet, the Coast Guard’s formula below shows how the rating is worked out. According to BoatUS, exceeding the listed capacities is not a federal violation for the owner, but many states prohibit carrying more people and gear than the plate allows or installing a motor above its horsepower limit, and exceeding the limits may void your insurance.
How Many People Can a Boat Hold?
Read the plate first. For a boat without one, the Coast Guard’s boater’s guide suggests checking with the manufacturer, finding a sister boat of the same model, or hiring a naval architect or marine engineer, and gives a rule of thumb that assumes 150-pound people and ignores the hull’s displacement:
Maximum number of persons = boat length (ft) × boat width (ft) ÷ 15
A 16-foot boat 6 feet wide gives 16 × 6 ÷ 15 = 6.4, so about 6 people, or 900 pounds at 150 pounds each. The guide doesn’t say how to round; the calculator rounds down, so it never adds a person.
Maximum Horsepower Formula (33 CFR 183.53)
For outboard monohulls under 20 feet, the builder computes a factor: boat length × maximum transom width, in feet. If the boat has no full transom, the width is the broadest beam in the aftmost quarter of its length. Up to a factor of 52.5, the horsepower comes from a table:
| Factor (nearest whole number) | Maximum horsepower |
|---|---|
| 0 to 35 | 3 hp |
| 36 to 39 | 5 hp |
| 40 to 42 | 7.5 hp |
| 43 to 45 | 10 hp |
| 46 to 52 | 15 hp |
A flat-bottom boat with hard chines and a factor of 52 or less goes one step lower, such as 5 hp instead of 7.5. Over a factor of 52.5, a formula applies, and a result that is not a multiple of 5 may be raised to the next multiple of 5:
- Remote steering and a transom at least 20 inches high: 2 × factor − 90.
- No remote steering, or a transom under 20 inches, on a flat-bottom hard-chine boat: 0.5 × factor − 15.
- No remote steering, or a transom under 20 inches, on any other boat: 0.8 × factor − 25.
For example, a 16-foot boat with a 6-foot transom has a factor of 96. With remote steering and a 20-inch transom, that is 2 × 96 − 90 = 102, raised to 105 hp. With a tiller it is 0.8 × 96 − 25 = 51.8, raised to 55 hp, or 0.5 × 96 − 15 = 33, raised to 35 hp, for a flat-bottom hard-chine hull. A 14-foot boat with a 3-foot transom has a factor of 42: 7.5 hp, or 5 hp with a flat bottom and hard chines. Boats 13 feet or shorter with remote wheel steering, a minimum transom height and room for no more than two people may instead be rated by a performance test, up to 40 hp.
Maximum Weight Capacity Formulas
The weight capacity on the plate comes from the boat’s maximum displacement: the weight of the water the hull displaces when it is immersed level to the point where water would come aboard. Boat weight is the hull, deck and superstructure, the permanent fittings and full built-in fuel tanks (without the tanks for boats rated for oars, paddles or 2 hp or less).
- Outboard boats (183.35): (maximum displacement − boat weight) ÷ 5. With a maximum displacement of 5,000 pounds and a boat weight of 500 pounds, that is 900 pounds.
- Inboard and sterndrive boats (183.33): the greater of maximum displacement ÷ 5 − boat weight ÷ 5 − 4 × machinery weight ÷ 5, and (maximum displacement − boat weight) ÷ 7. Machinery is the installed engines, controls, drive units and batteries. At 12,000, 3,000 and 800 pounds, the two give 1,160 and 1,285 pounds, so the capacity is 1,285 pounds.
- Boats rated for oars, paddles or 2 hp or less (183.37): 3 × (maximum displacement − boat weight) ÷ 10. At 1,500 and 150 pounds, that is 405 pounds.
How the Plate’s Persons Number Is Set
The persons capacity in pounds is at most the weight capacity, on an outboard boat less the motor, controls, battery and a full portable fuel tank; a boat with less than 550 pounds of persons capacity is also tested afloat with weights added along one side. The number of people is then at most the pounds plus 32, divided by 141 and rounded to the nearest whole number: 990 pounds allows (990 + 32) ÷ 141 = 7.2, so 7 people. Builders may mark fewer.
Pontoon Boats and Boats 20 Feet or Longer
The federal capacity rules cover monohull boats under 20 feet, and the regulation names the pontoon boat as an example of a boat that is not a monohull. Builders publish their own capacities: Starcraft lists its EX 20 R, 22 R and 24 R pontoon boats for 9, 10 and 12 people (1,315, 1,395 and 1,675 pounds). The rule of thumb doesn’t fit them well: for the EX 20 R, 20 feet 10 inches long and 8 feet 6 inches wide, it gives 11 people, two more than Starcraft’s figure.
To see what your load weighs, use the Boat Weight Calculator; fuel in portable tanks counts against the weight capacity, and the Fuel and Water Weight Calculator converts it to pounds. For the speed you can expect within your horsepower limit, try the Boat Speed Calculator.
Frequently Asked Questions
What does a capacity plate indicate?
The maximum number of people the boat may carry, as a number and in pounds, the maximum total weight of persons, motor and gear (persons and gear on inboard and sterndrive boats) and, on outboard boats, the maximum horsepower. Federal rules require it on monohull boats under 20 feet, except sailboats, canoes, kayaks and inflatable boats.
Where can you find the maximum horsepower for your boat?
On the boat’s capacity plate, which must be clearly visible to the operator when getting underway; BoatUS says plates are generally on the inside of the transom or next to the helm. For a boat without a plate, ask the builder; for outboard monohulls under 20 feet, the Coast Guard formula in 33 CFR 183.53 gives the rating.
How do you calculate how many people a boat can hold?
For a boat without a capacity plate, the Coast Guard’s rule of thumb is length × width ÷ 15, in feet, based on 150-pound people: a 16-foot boat 6 feet wide carries about 6. It ignores the hull’s displacement, so the plate or the builder’s figure comes first.
What length of boat requires a capacity plate?
Monohull boats less than 20 feet long, except sailboats, canoes, kayaks and inflatable boats (33 CFR 183.21). Longer boats and pontoon boats aren’t covered by that rule; check the builder’s capacity label or specifications.
How many people can fit on a pontoon boat?
As many as the builder rates it for: Starcraft lists its EX 20 R, 22 R and 24 R pontoons for 9, 10 and 12 people. Pontoon boats are not monohulls, so the federal capacity rules don’t cover them, and the length × width ÷ 15 rule of thumb would give 11 people for the 20-foot model, more than Starcraft’s 9.
Is it illegal to exceed a boat’s capacity?
It isn’t a federal violation for the owner, BoatUS notes, but many states prohibit carrying more people and gear than the plate allows or installing a motor above its horsepower limit, and exceeding the limits may void your insurance.