1. What is an Outboard Propeller Size Calculator?

Definition: This calculator estimates the optimal propeller diameter for outboard motors based on engine horsepower and a design constant.

Purpose: It helps boat owners and marine mechanics select the right propeller size for optimal engine performance and efficiency.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( D \) — Propeller diameter (inches)
• \( HP \) — Engine horsepower
• \( C \) — Design constant (typically 10 for most outboards)

Explanation: The formula calculates the cube root of the horsepower-to-constant ratio to determine the optimal propeller diameter.

3. Importance of Proper Propeller Sizing

Details: Correct propeller sizing ensures maximum engine efficiency, proper boat speed, fuel economy, and prevents engine strain.

4. Using the Calculator

Tips: Enter the engine horsepower and design constant (default 10). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's the typical design constant value?
A: Most outboard motors use a constant of 10, but this may vary based on specific engine designs.

Q2: Does this calculate pitch as well?
A: No, this calculates diameter only. Pitch depends on boat type and desired performance characteristics.

Q3: When would I change the constant value?
A: Adjust for high-performance engines (lower constant) or heavy-duty applications (higher constant).

Q4: How accurate is this calculation?
A: It provides a good starting point, but final propeller selection should consider boat weight, hull type, and usage.

Q5: What about multi-engine setups?
A: Calculate for each engine separately, as each will need its own properly sized propeller.