Multi-blade Propeller ALUM.AMITA4 13.80X21 Right-hand

Function and technical context

This four-bladed aluminum propeller with dimensions 13.80×21 and right-hand rotation acts as the final element in the hydrodynamic transmission chain, converting engine torque into direct thrust on the water. Its four-bladed geometry, unlike conventional three-blade designs, distributes the load more uniformly with each revolution, resulting in lower structural vibration, better acceleration response from a standstill, and greater efficiency in the medium-load working range. The internal hub transfers the rotation of the propeller shaft to the blades, being the critical point for impact absorption when striking submerged objects. Deterioration in the blade leading edge profile, in the hub, or in the trailing edge causes sustained cavitation, progressive loss of thrust, increased fuel consumption, and overstress on the shaft bearings, increasing the risk of serious damage to the lower unit transmission.

When to replace this component?

The most common symptoms indicating the need for replacement are: abnormal and perceptible vibration in the lower unit during navigation, noticeable loss of top speed or inability to reach the manufacturer's recommended rpm working range, excessive cavitation visible at the stern, and loss of bite on acceleration. It is recommended to visually inspect the propeller at the beginning and end of each boating season, checking the condition of the blades for bending, cracks, cavitation erosion or impact damage, as well as wear of the internal hub and drag bushing. Replacing the propeller preventatively at the first sign of structural damage avoids overloading the propeller shaft, seals, and bevel gear of the lower unit, preventing much costlier repairs and failures while underway.

Compatible Johnson/Evinrude Engines

Equivalent manufacturer part numbers