Boat Capacity Plate

Ian Fortey by Ian Fortey Updated on April 20, 2021. In

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Chapter III – The Boat

Section 7 – Boat Capacity Plate

Boat Capacity Plate

Boat builders must comply with Federal law by putting a Capacity Plate in sight of the helm (steering area) on motorized boats less than 20 feet in length. This plate displays three important items: the maximum weight of persons on board in pounds, the maximum carrying weight of the vessel in pounds and the maximum horsepower recommended for the boat.

boating safety course Capacity Plate

Should you own a boat which was built prior to the Federal law mandating capacity plates or have a homemade boat, the following formulas can be used to determine safe loading capacity.

Formulas for Safe Loading

Horsepower Capacity
for small, flat-bottom boats:
Multiply boat length (ft) times transom width (ft)
Person Capacity:
Average weight per person is 150 lbs.

If answer is:
35 or less

Maximum HP is:

(Boat length
Boat width)

Number of

Note: for flat bottom, hard chine boats, with an answer of 52 or less, reduce one increment (e.g. 5 to 3) Boat length and width are measured in feet. Round fractions down to next lower number.

Always check the capacity plate to make sure you are not overloading or over-powering the vessel. A motor larger than recommended will make the stern too heavy and can cause the boat to flip. The transom will ride too low in the water and you could be swamped by your own wake or a passing boat’s wake. Your boat will not sit properly in the water and will be difficult to handle.

Too many people (and/or gear) will also cause the boat to become unstable. Always balance the load so that your vessel maintains proper trim. Too much weight to one side or the other will cause the boat to list and increase the chance of taking on water. Too much weight in the bow causes the vessel to plow through the water and too much weight in the stern will create a large wake. All of these situations make the vessel difficult to handle and susceptible to swamping.

Remember that the capacity plate limits are suitable for normal operating conditions. In rough seas, bad weather or when operating in congested areas you will want to carry a lighter load.


1 Comment

  • Ken Donnelly on September 14, 2020

    I have a 24′ X 10′ home built tritoon. I want to power-up the tritoon with at least a 200HP, do I need a capacity plate? If so, how do I go about getting this tritoon re certified with a new plate?


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