Study of Propeller Cavitation and Its Effects on Vessel Speed in Nigerian Coastal Vessels

Propeller cavitation is a hydrodynamic phenomenon that significantly reduces propulsive efficiency, accelerates propeller erosion, and generates structural vibrations in marine vessels. This study examines the occurrence of propeller cavitation and its measurable effects on vessel speed and structural integrity among coastal trading vessels operating along the Nigerian shoreline between Badagry and Brass. Using a descriptive case study design, data were gathered through vibration measurements, vessel log reviews, underwater inspection reports, and interviews with marine engineers attached to selected shipping companies. Ten coastal vessels were purposively selected based on reported propulsion anomalies. The study finds that cavitation is prevalent among vessels with propellers that have not been re-pitched or repaired within the recommended five-year cycle, and that vessel speed reductions of between eight and fifteen percent are commonly associated with cavitation damage. Extensive blade erosion was documented on three of the sampled vessels, suggesting long-term neglect of propeller maintenance. Contributing factors include the practice of overloading vessels beyond their design displacement and the use of improperly matched propellers following engine replacements. The research recommends mandatory propeller inspection at each dry-docking cycle, use of cavitation-resistant alloys in propeller fabrication, and training of marine engineers in propeller performance assessment. Findings are directly applicable to vessel operators across Nigeria's coastal trade routes. Keywords: propeller cavitation, vessel speed, coastal vessels, propeller erosion, marine propulsion