Mercury - 300 Hour Maintenance Kit FourStroke Service Package Complete OEM Components 8M0097855. Overview. There's a certain comfort that comes from knowing your outboard is properly cared for-the kind of confidence that settles in right before you throttle up at dawn, or when you're easing home after a long day on the water. Routine maintenance is part of that peace of mind, and having everything you need in one place makes the job feel less like a chore and more like an investment in every fut