Enter your engine horsepower, boat weight, and desired speed into the calculator to determine the appropriate prop size for your boat.

## Prop Size Calculation Formula

The following formula is used to calculate the appropriate prop size for your boat.

Prop Diameter = (Boat Weight / Engine Horsepower) * (1 / Desired Speed)

Variables:

- Prop Diameter is the diameter of the propeller in inches
- Boat Weight is the weight of the boat in pounds
- Engine Horsepower is the horsepower of the boat’s engine
- Desired Speed is the speed you wish to achieve in miles per hour

To calculate the prop diameter, divide the boat weight by the engine horsepower, multiply the result by the inverse of the desired speed, and you’ll get the prop diameter in inches.

## What is Prop Size Calculation?

Prop size calculation refers to the process of determining the most suitable propeller size for your boat based on its weight, engine horsepower, and desired speed. Proper prop size calculation ensures optimal performance and fuel efficiency.

## How to Calculate Prop Size?

The following steps outline how to calculate the prop size using the given formula.

- First, determine your boat weight, engine horsepower, and desired speed.
- Use the formula: Prop Diameter = (Boat Weight / Engine Horsepower) * (1 / Desired Speed).
- Calculate the prop diameter by plugging in the values.
- Verify your calculation with the advanced prop size calculator for more precise results.
- Use the calculated prop diameter to choose the right propeller for your boat.

**Example Problem:**

Use the following variables as an example problem to test your knowledge.

Engine Horsepower = 200 HP

Boat Weight = 3500 lbs

Desired Speed = 40 mph

Using the formula: Prop Diameter = (3500 / 200) * (1 / 40) = 0.4375 inches

## FAQ

**1. What is prop diameter?**

Prop diameter is the diameter of the circular path the propeller blades make when rotating. Itâ€™s measured from the tip of one blade to the tip of the opposite blade.

**2. How does prop size affect boat performance?**

The size of the prop affects the boat’s acceleration, top speed, and fuel efficiency. A properly sized prop ensures optimal performance.

**3. How often should I check my prop size?**

It’s a good idea to check your prop size whenever you notice a change in performance or when making significant changes to your boatâ€™s weight or engine.

**4. Can this calculator be used for different types of boats?**

Yes, you can use this calculator for various types of boats by adjusting the input values to match the specifications of your boat.

**5. Is the calculator accurate?**

The calculator provides an estimate based on the inputs provided. For exact figures, itâ€™s best to consult with a marine technician or refer to your boat’s manual.