LOWER SEAL CRANKSHAFT YAMAHA 93102-25M28

Function and technical context

The lower crankshaft seal is a critical component of the engine's sealing system that prevents oil leakage from the casing to the outside. Located at the bottom of the crankshaft, this seal acts as a waterproof barrier between the inside of the engine and the external environment, ensuring that the lubricant stays where it belongs. Its deterioration allows the oil to progressively escape, reducing the lubrication of the internal engine components and exposing the system to the entry of salt water and contaminants. In boats, a failure in this seal can compromise the integrity of the engine in a matter of hours of operation, especially during navigation in rough waters.

When to replace this part?

Typical symptoms of wear include visible oil stains under the engine, a decrease in lubricant level without apparent cause, and a burning smell coming from the underside of the crankshaft. Although there is no fixed maintenance interval in hours of operation, it is recommended to inspect the condition of the seal during each seasonal service, especially if the engine has been idle or exposed to high humidity conditions. Preventive replacement prevents costly repairs resulting from loss of lubrication and water entering the crankcase, problems that can prematurely render the engine unusable.

Equivalent manufacturer part numbers