3-Blade Propeller 7 1/4X6 48-815083

Function and Technical Context

This three-blade propeller in high-resistance plastic, with a diameter of 7 1/4 inches and pitch 6, acts as the propulsion element of the transmission system in low-horsepower outboard motors, converting the rotational torque of the shaft into hydraulic thrust to propel the vessel. It operates in the lower propulsion unit, directly coupled to the output shaft of the gearbox, so any imbalance in the blades is transmitted directly to the seals, bearings, and bevel gears of the transmission. The three-blade geometry is optimized to maximize acceleration during port departure and maintain efficient cruising speed in lightweight vessels—auxiliary boats, inflatables, or dinghies—with motors up to 5 HP. The high-resistance plastic used in its manufacture offers a calculated balance between structural rigidity and impact absorption capacity, protecting the transmission against contact with the bottom or floating debris through controlled deformation before transmitting destructive loads to the shaft. A deteriorated propeller or one with altered geometry causes persistent cavitation, stern vibrations, motor overload, and premature shaft seal deterioration.

When to Replace This Part?

The clearest signs that the propeller requires replacement are: appreciable loss of top speed with no apparent motor cause, inability to reach the usual cruising speed, vibration or rattling at the stern during navigation, and difficulty getting the vessel to plane. In motors of 2 to 5 HP, even light impact against rocks, compacted sand, or hard seaweed can splinter or bend a plastic blade, altering rotational balance and causing accelerated wear on the shaft seals. Visual inspection of the propeller is recommended at the start of each boating season and after any grounding or contact with the bottom; replacing it preventively at the first sign of damage avoids failures in the lower transmission that are considerably more costly to repair.

Mercury / MerCruiser

Compatible Johnson/Evinrude Motors

Equivalent Manufacturer References