1. What is the Boat Speed Formula?

The boat speed formula (Crouch's formula) estimates a boat's maximum speed based on horsepower, displacement weight, and hull type. It provides a theoretical maximum speed for planning hull boats.

2. How Does the Calculator Work?

The calculator uses Crouch's formula:

Where:

• \( v \) — Boat speed (knots or mph)
• \( C \) — Crouch constant (150-200, unitless)
• \( HP \) — Shaft horsepower (hp)
• \( Weight \) — Displacement weight (lbs)

Explanation: The formula calculates theoretical hull speed based on power-to-weight ratio, with the Crouch constant accounting for hull efficiency.

3. Importance of Boat Speed Calculation

Details: Accurate speed estimation is crucial for boat design, performance prediction, engine selection, and understanding vessel capabilities for safe operation.

4. Using the Calculator

Tips: Enter shaft horsepower in hp, displacement weight in pounds, select Crouch constant (150 for displacement hulls, 190 for planning hulls, 200 for high-speed boats), and choose speed unit (knots or mph).

5. Frequently Asked Questions (FAQ)

Q1: What is the Crouch constant?
A: The Crouch constant represents hull efficiency - lower values for displacement hulls (150), higher for planning hulls (190-200).

Q2: Why use shaft horsepower instead of brake horsepower?
A: Shaft horsepower accounts for transmission losses and represents the actual power delivered to the propeller.

Q3: What are typical boat speeds?
A: Small boats: 20-40 mph, cruisers: 25-35 mph, high-performance boats: 50-100+ mph depending on design and power.

Q4: Are there limitations to this formula?
A: Less accurate for very light or heavy boats, air-resistance limited speeds, and non-planning hull designs.

Q5: How accurate is this calculation?
A: Provides theoretical maximum - actual speed depends on hull condition, propeller efficiency, water conditions, and load.