NUT 90170-12138 REC90170-12138

Function and technical context

This nut performs a critical securing and securing function on Yamaha and Mercury marine engines. It is part of the structural fastening systems of the engine block, guaranteeing the mechanical integrity of essential assemblies such as the cylinder, cylinder head and distribution components. Its correct installation and tightening prevents unwanted movements that could lead to coolant water leaks, loss of compression in the combustion chambers and, in serious cases, catastrophic damage to the internal structure of the engine during navigation at maximum load.

When to replace this part?

Engine mounting nuts require periodic inspection during seasonal maintenance checks, as continued vibration of the marine engine can cause gradual loosening or rust corrosion in saline environments. It is recommended to check the tightening torque and the condition of the thread at each seasonal inspection, and replace the nut if it presents deformation, damaged thread or signs of advanced corrosion that compromises its holding capacity. Preventive replacement of worn nuts before the boating season avoids costly emergency repairs and ensures structural engine safety under intensive boating conditions.

Equivalent manufacturer part numbers