1. What is a Marine Propeller Pitch Calculator?

Definition: This calculator determines the theoretical pitch of a marine propeller based on boat speed, engine RPM, and a conversion constant.

Purpose: It helps boat owners, mechanics, and marine engineers select the proper propeller for optimal performance.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( P \) — Propeller pitch (inches)
• \( S \) — Boat speed (miles per hour)
• \( C \) — Conversion constant (typically 1056)
• \( RPM \) — Engine revolutions per minute

Explanation: The speed multiplied by the constant converts to inches per minute, which when divided by RPM gives the theoretical advance per revolution (pitch).

3. Importance of Proper Propeller Pitch

Details: Correct propeller pitch ensures optimal engine performance, fuel efficiency, and prevents over-revving or lugging the engine.

4. Using the Calculator

Tips: Enter the boat speed in mph, conversion constant (default 1056), and engine RPM. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is the 1056 constant?
A: It converts mph to inches per minute (5280 ft/mile × 12 inches/ft ÷ 60 minutes/hour).

Q2: Why is theoretical pitch different from actual?
A: Slip (typically 10-15%) means the propeller doesn't advance as much as theoretically calculated.

Q3: When would I change the constant?
A: Only if using different units (e.g., km/h would require 1056 × 1.609 = 1698).

Q4: How do I measure boat speed accurately?
A: Use GPS speed for most accurate results, not paddle wheel or pitot tube speedometers.

Q5: What RPM should I use?
A: Use your engine's maximum recommended RPM at wide open throttle (WOT).