Mercury – Complete Water Pump Kit | 9.9–20hp EFI Series | Marine-Grade Components | 8M0135821Mercury Complete Water Pump Kit 9. 920hp EFI Series Marine Grade Components 8M0135821 Overview Theres a certain confidence that comes from knowing your outboards cooling system is truly up to the job. When youre running through a narrow channel on a rising tide or easing into a long stretch of open water, you want to trust that your engine is staying cool, steady, and protected. The Mercury Marine part 8M0135821 Complete Water Pump Kit gives you that