1. What is Mercury Prop Slip?

Prop slip is the difference between the theoretical distance a propeller should move the boat and the actual distance it moves, expressed as a percentage. It indicates the efficiency of the propeller in converting rotational power into forward motion.

2. How Does the Calculator Work?

The calculator uses the Mercury Prop Slip formula:

Where:

• \( Theoretical \) — Theoretical boat speed (mph)
• \( Actual \) — Actual measured boat speed (mph)

Explanation: The formula calculates the percentage difference between the ideal propeller performance and the actual performance, helping to assess propeller efficiency.

3. Importance of Prop Slip Calculation

Details: Calculating prop slip is essential for optimizing boat performance, fuel efficiency, and identifying potential issues with propeller selection or condition.

4. Using the Calculator

Tips: Enter theoretical speed and actual speed in mph. Both values must be valid (theoretical > 0, actual ≥ 0).

5. Frequently Asked Questions (FAQ)

Q1: What is a good prop slip percentage?
A: Generally, 10-15% slip is considered good for most boats. Higher percentages may indicate inefficiency or problems.

Q2: Why is my prop slip percentage high?
A: High slip can be caused by incorrect propeller size, damaged blades, hull fouling, or improper engine trim.

Q3: Can prop slip be negative?
A: No, prop slip cannot be negative as actual speed cannot exceed theoretical speed under normal conditions.

Q4: How does prop slip affect fuel consumption?
A: Higher slip percentages typically result in lower fuel efficiency as more energy is wasted in water displacement.

Q5: When should I recalculate prop slip?
A: Recalculate after changing propellers, after hull cleaning, or if you notice changes in boat performance.