90704-RCA-A00 Key (4.5x24) - Overview. The 90704-RCA-A00 Key (4.5x24) is a critical OEM component designed specifically for Honda marine engine systems. Functioning within the crankshaft and piston assembly, this key ensures reliable mechanical engagement and precise alignment of rotating parts. Engineered to meet strict Honda factory specifications, it plays a vital role in maintaining smooth engine operations. Its OEM manufacturing ensures seamless integration with existing parts, maintaining