Mercury - Quicksilver 8M0204712 Water Pump Impeller 15-25HP Outboard Cooling System Marine Elastomer Construction 8M0204712. Overview. There's a certain comfort in knowing your outboard is staying cool no matter what kind of water you're running through. When you're pushing across a windy bay or idling down a narrow creek, you want that steady cooling flow you don't have to think twice about. This Mercury Marine part delivers exactly that kind of peace of mind. It's one of those hidden component