Mercury - Fuel Pump Cooler Kit EFI Fuel System Cooling 8M0125852. Overview. Fuel heat can sneak up on EFI engines, especially when you're running hard or sitting in warm conditions. That's where the Mercury Fuel Pump Cooler Kit 8M0125852 comes into play. This kit is designed to help manage fuel temperature on select MerCruiser EFI sterndrive and inboard engines, keeping fuel delivery more consistent and combustion more efficient. It's a behind-the-scenes component, but one that can make a real d