1. What is Propeller Pitch?

Propeller pitch is the theoretical distance a propeller would move forward in one revolution if it were moving through a soft solid medium (like a screw through wood). It's a crucial parameter in propeller design and selection.

2. How Does the Calculator Work?

The calculator uses the propeller pitch formula:

Where:

• Speed — Boat speed through water in knots
• RPM — Engine/propeller revolutions per minute
• Slip Factor — Typically 0.7-0.9 (15-30% slip is common)

Explanation: The formula calculates how much forward movement would occur per revolution, accounting for propeller slip (the difference between theoretical and actual movement).

3. Importance of Proper Propeller Sizing

Details: Correct propeller pitch and diameter are essential for optimal engine performance, fuel efficiency, and preventing engine overload or underutilization.

4. Using the Calculator

Tips: Enter your boat's speed in knots, engine RPM at that speed, and estimated slip factor (start with 0.85 for average boats). The calculator will estimate pitch and suggest a diameter.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical slip factor?
A: Most boats have 10-30% slip (factor 0.7-0.9). Displacement hulls have higher slip than planing hulls.

Q2: How accurate is the diameter estimate?
A: The 2.5×pitch rule is approximate. Actual diameter depends on blade design, boat type, and engine power.

Q3: Why does pitch matter?
A: Too much pitch overloads the engine; too little underutilizes it. Correct pitch keeps RPM in optimal range.

Q4: Should I measure speed through water or over ground?
A: Use speed through water (from paddlewheel, not GPS) for accurate calculations.

Q5: How do I know if my current prop is wrong?
A: If engine can't reach rated RPM at full throttle (too much pitch) or exceeds it (too little pitch).