Mercury - 300 Hour Maintenance Kit 3.4L V6 FourStroke Series OEM Components 8M0149930. Overview. Ask anyone who spends real time on the water - the kind of boater who racks up hours chasing tide changes, hauling gear, or running a busy charter - and they'll tell you the same thing: long-term reliability doesn't happen by accident. It's built through routine care and the right parts. The Mercury 8M0149930 300 Hour Maintenance Kit gives you that confidence you only get when you know your engine ha