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Boat Speed Formula:
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The Boat MPH Calculator estimates boat speed in miles per hour using engine RPM, propeller pitch, propeller slip percentage, and gear ratio. This calculation helps boat owners and marine enthusiasts optimize performance and efficiency.
The calculator uses the boat speed formula:
Where:
Explanation: The formula calculates theoretical boat speed based on propeller characteristics and engine performance, accounting for propeller slip which represents efficiency loss.
Details: Accurate speed calculation helps in propeller selection, fuel efficiency optimization, performance tuning, and ensuring the boat operates within its designed parameters.
Tips: Enter RPM as engine speed, propeller pitch in inches, propeller slip as percentage (typically 10-20% for efficient setups), and gear ratio from your marine transmission specifications.
Q1: What is propeller slip and why does it occur?
A: Propeller slip is the difference between theoretical and actual boat speed, caused by water resistance, cavitation, and inefficiencies in propulsion system.
Q2: What is a typical propeller slip percentage?
A: Well-tuned boats typically have 10-20% slip. Higher percentages indicate inefficiency, while very low percentages may suggest measurement errors.
Q3: How do I find my boat's gear ratio?
A: Check your outboard motor or sterndrive specifications, or consult your owner's manual. Common ratios range from 1.5:1 to 2.5:1.
Q4: Why is propeller pitch important?
A: Pitch determines how far the boat would move forward with each propeller revolution in ideal conditions, directly affecting speed and engine loading.
Q5: Can this calculator be used for all boat types?
A: Yes, but results are most accurate for planing hulls. Displacement hulls may have different performance characteristics.