Boat Speed Calculator Prop

Boat Speed Formula:

\[ V = \frac{RPM \times PP \times (1 - \frac{PS}{100})}{GR \times 1056} \]

Engine RPM (RPM):

rev/min

Propeller Pitch (PP):

inches

Propeller Slip (PS):

Gear Ratio (GR):

dimensionless

Boat Speed (V):

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1. What is the Boat Speed Calculator?

The Boat Speed Calculator estimates vessel speed based on propeller specifications and engine parameters. It calculates theoretical speed while accounting for propeller slip, providing a realistic performance estimate.

2. How Does the Calculator Work?

The calculator uses the boat speed formula:

\[ V = \frac{RPM \times PP \times (1 - \frac{PS}{100})}{GR \times 1056} \]

Where:

\( V \) — Boat speed (mph)
\( RPM \) — Engine revolutions per minute (rev/min)
\( PP \) — Propeller pitch (inches)
\( PS \) — Propeller slip (%)
\( GR \) — Gear ratio (dimensionless)

Explanation: The formula calculates theoretical speed based on propeller advance per revolution, then adjusts for real-world efficiency loss through propeller slip percentage.

3. Importance of Boat Speed Calculation

Details: Accurate speed prediction helps in propeller selection, performance optimization, fuel efficiency planning, and ensuring the vessel operates within its designed performance envelope.

4. Using the Calculator

Tips: Enter engine RPM, propeller pitch in inches, propeller slip percentage (typically 10-20% for planing hulls), and gear ratio. All values must be positive with slip between 0-100%.

5. Frequently Asked Questions (FAQ)

Q1: What is propeller slip?
A: Propeller slip is the difference between theoretical and actual distance traveled per revolution, expressed as a percentage. It accounts for water displacement and efficiency losses.

Q2: What are typical propeller slip values?
A: Well-matched props: 10-15%, average: 15-20%, poor matching: 20%+. Displacement hulls have higher slip than planing hulls.

Q3: How does gear ratio affect speed?
A: Higher gear ratios reduce propeller RPM relative to engine RPM, affecting torque and speed. Proper ratio matching is crucial for optimal performance.

Q4: Why is propeller pitch important?
A: Pitch determines theoretical distance traveled per revolution. Higher pitch generally means higher top speed but slower acceleration.

Q5: Can this calculator be used for all boat types?
A: It works best for planing hulls with conventional propellers. Displacement hulls and specialized propulsion systems may require different calculations.