1. What is a Boat Speed Calculator?

Definition: This calculator estimates boat speed based on engine RPM, propeller pitch, and propeller slip factor.

Purpose: It helps boaters and marine professionals predict theoretical boat speed for propeller selection and performance tuning.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S \) — Boat speed (miles per hour)
• \( RPM \) — Engine revolutions per minute
• \( Pitch \) — Propeller pitch (inches)
• \( Slip \) — Propeller slip factor (decimal 0-1)

Explanation: The formula calculates theoretical speed by accounting for how much the propeller "slips" through the water (not achieving full pitch advancement per revolution).

3. Importance of Boat Speed Calculation

Details: Proper speed estimation helps with propeller selection, fuel efficiency calculations, and performance optimization.

4. Using the Calculator

Tips: Enter engine RPM, propeller pitch in inches, and slip factor (default 0.12 for average boats). Slip must be between 0 and 1.

5. Frequently Asked Questions (FAQ)

Q1: What is propeller slip?
A: Slip is the difference between theoretical and actual movement through water, caused by water not being a solid medium (typically 10-20% for most boats).

Q2: Where does the 1056 constant come from?
A: It converts inches per minute to miles per hour (12 inches/foot × 5280 feet/mile ÷ 60 minutes/hour).

Q3: What's a typical slip factor?
A: Most boats have 10-15% slip (0.10-0.15). High-performance boats may be lower (0.05-0.10), while heavily loaded boats may be higher (0.20-0.30).

Q4: How do I find my propeller pitch?
A: The pitch is usually stamped on the propeller hub or in the manufacturer's specifications (e.g., "14x19" means 14" diameter, 19" pitch).

Q5: Why is my actual speed different?
A: This calculates theoretical speed. Actual speed is affected by hull design, load, water conditions, engine condition, and other factors.