DIABOLO PROPELLER SEAL 91301-30M17

Function and technical context

The propeller diabolo seal is a critical component of the propeller shaft sealing system on outboard and outboard engines. Its main function is to prevent salt water from entering the gearbox and the internal cavities of the engine, maintaining lubrication pressure and protecting the transmission gears. It works at the interface between the rotating propeller shaft and the fixed structure of the engine, supporting both rotary movements and variable hydrostatic pressures. A failure in this seal allows seawater infiltration, which causes accelerated corrosion of internal components, loss of lubricant, rusting of gears and, ultimately, locking of the shaft and rendering the motor unusable.

When to replace this part?

Typical symptoms of diabolo seal wear include the presence of water or milky emulsion in the gearbox oil, loss of lubricant through dripping in the propeller shaft area, and visible corrosion or oxidation on surrounding components. It is recommended to check the condition of the seal during each seasonal maintenance, especially after prolonged navigation in salt water, and replace it preventively every 4-6 seasons or when any signs of degradation are observed. Preventive replacement of this component avoids costly repairs and immobilization of the boat in adverse conditions.

Equivalent manufacturer part numbers