1. What is Propeller Sizing?

Propeller sizing is the process of determining the optimal diameter and pitch of a boat propeller based on engine specifications, boat characteristics, and performance requirements. Proper propeller sizing ensures efficient power transfer from the engine to the water.

2. How Does the Calculator Work?

The calculator uses the following fundamental formula:

Where:

• \( HP \) — Engine horsepower
• \( RPM \) — Engine revolutions per minute
• \( K \) — Coefficient based on boat type (130-150)

Explanation: The formula calculates propeller diameter in inches based on power-to-RPM ratio, adjusted for boat type and speed.

3. Importance of Proper Propeller Size

Details: Correct propeller sizing maximizes efficiency, prevents engine over-revving or lugging, improves fuel economy, and ensures optimal boat performance.

4. Using the Calculator

Tips: Enter engine horsepower and maximum RPM. Select boat type and optionally enter typical cruising speed for more accurate results.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between diameter and pitch?
A: Diameter is the circle swept by the blade tips, while pitch is the theoretical forward movement per revolution.

Q2: How does boat speed affect prop size?
A: Faster boats typically need larger diameter props with higher pitch to efficiently transfer power at speed.

Q3: What if my actual prop size differs from calculation?
A: This calculator provides a starting point. Final selection should consider actual performance tests and manufacturer recommendations.

Q4: How important is boat weight in prop selection?
A: Very important. Heavier boats may need larger diameter props with lower pitch to get on plane.

Q5: Should I consult a professional for prop selection?
A: For critical applications or high-performance boats, professional advice is recommended.