Mercury - Water Pump Repair Kit Cooling System Service Complete 7-Piece Kit 89981T1. Overview. If you spend enough time running a small Mercury or Mariner outboard, you learn just how tough these little engines are. They'll push a boat all day long on very little fuel, and they rarely complain - unless the cooling system starts to lose efficiency. That's usually when you first notice a weak telltale or a slight rise in temperature. The Mercury 89981T1 Water Pump Repair Kit gives your engine a fr