Mercury - Command Thrust 300 Hour Maintenance Kit FourStroke Service Pack Precision Marine Components 8M0120867. Overview. There's a certain comfort that comes from knowing your outboard is ready for whatever the day brings-smooth tides, choppy water, long drifts, or a quick run back to the dock before the weather turns. When you own a small but hardworking Mercury FourStroke, routine maintenance isn't just a box to check; it's part of the rhythm of boating. You service your engine because you t