Mercury - 300 Hour Maintenance Kit FourStroke EFI Service Package Complete OEM Components 8M0097857. Overview. Every boater knows that when you hit that 300-hour mark, you're not just doing another routine service-you're giving your engine the deep care it needs to carry you confidently into the next season. The Mercury 8M0097857 300 Hour Maintenance Kit brings that sense of reassurance together in one thoughtfully assembled package. Designed specifically for Mercury 1.7L 75-115 horsepower FourS