Boat Speed Formula:
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Definition: This calculator estimates a boat's theoretical top speed based on propeller specifications and engine RPM.
Purpose: It helps boaters and marine professionals determine expected performance and select appropriate propellers.
The calculator uses the formula:
Where:
Explanation: The formula calculates theoretical speed by accounting for how much the propeller "slips" in the water.
Details: Proper propeller selection affects fuel efficiency, engine life, and overall boat performance. This calculation helps optimize these factors.
Tips: Enter engine RPM, propeller pitch (distance propeller would move in one revolution in a solid medium), and slip factor (default 0.12). Slip must be between 0 and 1.
Q1: What is propeller slip?
A: Propeller slip is the difference between theoretical and actual movement through water, caused by water not being a solid medium.
Q2: What's a typical slip factor?
A: Most boats have 8-15% slip (0.08-0.15). High-performance boats may be lower, while heavily loaded boats may be higher.
Q3: Why 1056 in the formula?
A: This constant converts inches per minute to miles per hour (12 inches/foot × 5280 feet/mile ÷ 60 minutes/hour).
Q4: How do I find my engine's maximum RPM?
A: Check your engine specifications or use a tachometer at wide-open throttle with normal load.
Q5: Does this account for hull design or load?
A: No, this is theoretical speed. Actual speed depends on hull efficiency, weight, water conditions, and other factors.