90704-PNA-000 Key (4.5X21) - Overview. The 90704-PNA-000 Key (4.5X21) is a precision-engineered component for Honda marine engine systems. This crankshaft key is designed to align and secure rotating parts, ensuring accurate mechanical motion within the engine system. As a compact and essential piece, it plays a vital role in maintaining reliable power transmission and engine timing. Built to meet strict factory specifications, it ensures seamless integration with existing parts, maintaining opt