How to Load Your Boat Safely: Capacity Plate, Balance and Stability

The BoatUS Foundation breaks it down by boat type:

• Outboard boats: maximum persons (in people and in pounds), maximum weight capacity (people, motor and gear), and maximum horsepower.
• Inboard and sterndrive boats: maximum persons and maximum weight capacity (people and gear). There's no horsepower line, because the federal powering standard doesn't apply to them.
• Manually propelled boats (rowboats and the like): persons and weight.

Photograph the plate and keep the picture on your phone.

The "persons" number is calculated from the pounds figure using a fixed formula in 33 CFR 183 that works out to roughly 140 lb per person. Many adults weigh a lot more than that. Five 200-lb adults is 1,000 lb, even if the plate says "6 persons or 900 lb." Whichever limit you hit first is the limit.

The persons capacity also isn't arbitrary: the federal test loads weight along one side of each seating area until the boat reaches its maximum safe list or trim without taking water. In other words, the plate already assumes people won't all stay perfectly centered.

For the maximum weight number, count everything you carry:

• People (be honest)
• On an outboard boat, the motor and controls (check the plate's wording)
• Coolers with ice and drinks, tackle, anchors and rode, tubes, skis, dive gear
• Extra fuel cans: gasoline weighs about 6 lb per gallon
• Water: about 8 lb per gallon (Load Rite uses that figure for trailer sizing). A livewell or bait tank full of water is real weight.

BoatUS also warns that older boats tend to gain weight over the years, from gear that never leaves and from hulls or foam that have absorbed water. If your boat sits lower than it used to with the same load, see our waterlogged foam guide.

BoatUS points out that safe passenger loading depends on the number of real seating positions underway. Two slim adults with four or five small kids in a boat designed to seat four can be dangerous, even if the total weight is well under the plate. The BoatUS Foundation adds that the number of seats doesn't automatically equal how many people the boat can safely carry, either. Use both: plate limits and real seats.

On outboard boats, don't exceed the maximum horsepower on the plate. The BoatUS Foundation says many states make it illegal to carry more than the plate allows or to install a motor over the horsepower limit, and that exceeding the limits may void your insurance. BoatUS also notes that repowering an older boat with a modern four-stroke can add 10 to 15 percent more weight at the transom than the boat was designed for, enough to let water back into the cockpit. Our repowering guide covers how to check before you buy.

Spread people and heavy gear evenly on both sides. BoatUS's example: everyone rushing to one side to look at a whale can push a gunwale down far enough to let water pour in. If someone moves to one side to fish, land a fish or climb aboard, have someone else shift the other way, and slow down first.

How weight is spread fore and aft changes how the boat rides:

• Too much in the stern: the boat squats, the bow rises and it's harder to see ahead. BoatUS warns that many older outboard boats have low transom cutouts that can flood when the boat slows quickly with extra weight aft. Newer boats usually have a motor well that reduces this risk.
• Too much in the bow: the boat plows, takes spray or waves over the bow and can steer badly at speed.
• Aim for the boat to sit close to level at rest, then fine-tune with trim and trim tabs once you're running, not by moving people around at speed.

• The higher the weight, the less stable the boat. BoatUS notes that anglers and hunters can make a small boat unstable just by standing up.
• Keep people seated on real seats while underway: not on gunwales, the bow, seat backs or engine covers.
• Store heavy items low, near the centerline, and strapped down so they can't slide to one side in a turn.
• The BoatUS Foundation reminds owners that people are a "live" load: shift people and weight only after you've stopped or slowed.

• Upper decks and flybridges put weight high. BoatUS reported on a 34-foot cabin cruiser that rolled over after fireworks with 27 people aboard, eight of them on the flybridge; a naval architect's analysis found it had almost no reserve stability with that load. On boats with an upper deck, keep only a few people up top, especially in crowded wakes.

• Water sloshing in the bottom of the boat reduces stability, and BoatUS says a wave or wake can then flip it. Keep the bilge pumped out.
• Cockpit drains: on boats with scuppers, BoatUS warns that one heavy friend or a second cooler can be enough to make water come back in through the drains. Watch the scuppers after you load; if water is coming in at rest, you're too heavy or too far aft.
• Livewells and fittings: BoatUS found leaking livewell plumbing and open livewell valves behind several sinkings. Know where your through-hull valves are and close them when not in use.
• Drain plug: BoatUS suggests tying the drain plug to the boat key so you can't forget it.
• If your boat's cockpit drains into the bilge, remember that bilge pumps are for nuisance water, not for keeping a swamped boat afloat.

The capacity plate assumes good to moderate weather. The BoatUS Foundation says to keep the load well below the limit in rough water, and BoatUS notes small boats with a full load can be overwhelmed by modest waves or even a large wake.

• Carry fewer people and less gear when wind or waves are up, or in heavy boat traffic.
• Take big waves and wakes bow-first and at a slow, steady speed.
• If a squall hits, BoatUS says to have passengers stay low near the center of the boat while you head in.
• Anchor from the bow, never the stern; a stern anchor plus a wave can pull the low transom under.

• Riders count when they climb back in. Plan the load with everyone aboard, including the person on the tube or skis and their wet gear.
• Seat the spotter where they can watch the rider without standing on a seat or sitting on the gunwale.
• When a rider comes back aboard, shut the engine off and have the rest of the crew stay forward and centered so the stern doesn't squat.
• Ballast: on wake boats, full ballast tanks plus a full crew can take you near or past the boat's limits. Check the builder's manual and our wake boat ballast guide before adding ballast bags.

With everyone and everything aboard:

• Is the boat sitting close to level, side to side and front to back?
• Is there reasonable freeboard all around, and no water coming in through scuppers or the transom cutout?
• Is the drain plug in and the bilge pump working?
• Is everyone seated, with life jackets on or within reach (on smaller boats, on)?

If any answer is no, move or remove weight before you go.