Outboard Engine Size Calculator
Estimated Horsepower Requirements
Recommended Engine Size: HP
Minimum Safe Power: HP
Performance Power: HP
How to Determine the Right Horsepower for Your Boat
Choosing the correct outboard motor is a balance between performance, fuel efficiency, and safety. Underpowering a boat is a common mistake that leads to the engine working too hard, resulting in poor fuel economy and difficulty reaching a "plane."
The Power-to-Weight Ratio
The industry standard for a planing hull is generally between 1 HP for every 25 to 40 pounds of total weight. Total weight must include:
- Dry Hull Weight: The manufacturer's stated weight.
- Fuel: Approximately 6.1 lbs per gallon.
- Passengers: Average weight of all people onboard.
- Gear: Batteries, anchors, coolers, and fishing tackle.
Hull Type Impact
Different hulls create different amounts of drag. A flat-bottom boat planes easily and requires less power. Conversely, a pontoon boat has significant surface area and wind resistance, requiring more horsepower to achieve the same speed as a monohull. Deep-V hulls slice through waves better but require more "push" to overcome water displacement.
Practical Example
If you have a 16-foot fiberglass V-hull boat that weighs 1,200 lbs dry, adds 300 lbs of fuel/gear, and carries two 200 lb passengers, your total weight is 1,900 lbs.
- Casual Use (1:40 ratio): 1,900 / 40 = 47.5 HP. A 50 HP motor is appropriate.
- Watersports (1:25 ratio): 1,900 / 25 = 76 HP. A 75 HP or 90 HP motor would be ideal.
Why Minimum Horsepower Matters
If you underpower your vessel, you may find that the boat "plows" through the water rather than lifting onto a plane. This creates massive drag, increases fuel consumption significantly, and makes the boat difficult to steer in rough conditions or following seas.