How to Determine the Horsepower of an Outboard Motor

A boat has a maximum weight limit in order to travel safely on the water. The boat also has a horsepower rating. A boat hull design greatly affects the maximum horsepower rating. Designers and manufactures build boats to specific calculations, but you may use your boat for a different purpose.

Use the manufacturer's suggestions first and then simply make calculations based upon the boat use to determine the horsepower of your outboard motor.

Step #1:

Search the interior of the stern until you find the National Marine Manufacturers Association Certification plate. Review the recommended limit of passengers as well as the horsepower rating. The horsepower rating determines the largest outboard motor to use for your boating needs.

Step #2:

Multiply the maximum horsepower rating on the plate by 1.10 to determine the size of the outboard motor needed. For example, if the maximum horsepower rating is denoted as 110, multiply by 1.10 to reach a final horsepower of 121 or 120. In this example you round down due to the horsepower being rated in multiples of 10. The additional 10 percent of horsepower makes it easier to carry a load of several passengers and equipment.

Step #3:

Calculate the equation in the opposite direction if you boat alone. Take the maximum horsepower rating from the plate. Take the maximum horsepower rating from the above example and divide by 1.10, 110/1.10 equates to a maximum horsepower rating of 100. The performance will generally be the same from a 110 horsepower outboard motor as a 100 horsepower outboard motor.

Following the steps allows boat owners to maximize the performance of their boats. Ensure the right size horsepower is selected correctly to avoid damaging the boat and placing all of the passengers in danger.

A key tip to remember is to always follow the suggested horsepower rating supplied by the manufacture of the boat.