Mercury - Water Pump Assembly MerCruiser Cooling System Aluminum & Marine Composite 8M0113735. Overview. If you spend enough time on the water, you learn to appreciate the parts you never want to think about - the ones that quietly keep your engine running cool while you're busy soaking in the breeze or watching the horizon roll by. A dependable water pump becomes one of those silent partners in every good day on the water. The Mercury 8M0113735 Water Pump gives you that same steady reassurance.