35490-ZY9-004 Oil Pressure Switch - Overview. The 35490-ZY9-004 Oil Pressure Switch is a vital component in Honda marine engine systems. It serves to monitor and signal the oil pressure within the engine, providing crucial alerts when oil pressure falls below safe operating levels. This switch supports the oil system, ensuring the engine operates reliably and is protected from damage due to low oil pressure. By integrating seamlessly with existing engine parts, it maintains optimal performance a