Propeller Efficiency

MPH = 0.0009469 * Pitch * RPM * Efficiency

Or

KPH = 0.0008234 * Pitch * RPM * Efficiency

Where:

• MPH is Statute Miles Per Hour
• KPH is Knots Per Hour
• Pitch of the Propeller
• RPM is the Revolution of the Propeller (make sure you convert for your transmission reduction)
• Efficiency is expressed as a Percent

Example: Solving for efficiency.

1. %E=KPH/(.0008234*Pitch*RPM)
2. %E=8.05/(.0008234*30*489.8)
3. %E=66.53% (42 Nordic Tug with 2.45 reduction)

Full Displacement Hull Speed

Knots = 1.34 * √LWL

Where:

• Knots is the full displacement speed expressed in Knots per Hour
• √ is the square root
• LWL is the waterline length

Example: Solving for Hull Speed

1. Knots=1.34*√40.5
2. Knots=8.53