87121-ZW9-S00 Rr (9.9) Mark - Overview. The 87121-ZW9-S00 Rr (9.9) Mark is a genuine OEM component for Honda marine engine systems, specifically tailored to the 9.9 horsepower model range. This marking part supports the engine identification system, playing a crucial role in maintaining accurate labeling and tracking of your Honda marine engine parts. Designed to Honda's exact factory specifications, it integrates seamlessly with existing hardware, preserving the overall system's optimal perform