1. What is Propeller Pitch?

Propeller pitch is the theoretical distance (in inches) that a propeller would move forward in one revolution if it were moving through a soft solid medium without slip. It's a crucial factor in boat performance.

2. How Does the Calculator Work?

The calculator uses the propeller pitch equation:

Where:

• \( Engine\ RPM \) — Engine revolutions per minute
• \( Slip\ Factor \) — Propeller slip (typically 0.10-0.20)
• \( Gear\ Ratio \) — Transmission gear reduction ratio
• \( Speed \) — Boat speed in miles per hour
• 88 — Conversion factor (feet to miles and minutes to hours)

Explanation: The equation calculates the theoretical propeller pitch needed to achieve a certain speed at given engine RPM, accounting for gear reduction and propeller slip.

3. Importance of Proper Pitch

Details: Correct propeller pitch ensures optimal engine RPM at cruising speed, maximizes fuel efficiency, and prevents engine over-revving or lugging.

4. Using the Calculator

Tips: Enter actual measured values for best results. For slip factor, use 0.10-0.15 for average boats, 0.15-0.20 for heavy or high-drag boats.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical slip factor?
A: Most boats have 10-20% slip. High-performance boats may be 5-10%, while heavily loaded or inefficient hulls may approach 25%.

Q2: How does pitch affect performance?
A: Higher pitch reduces engine RPM at given speed, while lower pitch increases RPM. Too high pitch may overload engine, too low may prevent reaching full RPM.

Q3: What if my actual speed differs from calculated?
A: Adjust slip factor accordingly and recalculate. Actual performance depends on hull design, load, and water conditions.

Q4: Can I use this for inboard and outboard engines?
A: Yes, the calculation works for all propeller-driven boats, though slip factors may vary between propulsion types.

Q5: How precise does pitch need to be?
A: Propellers typically come in 1-2 inch pitch increments. Choose the closest available to your calculated value.