Mercruiser Gen II Water Pump Kit | Sierra 18-3147 Sierra replacement water pump kit for Mercruiser Alpha I Gen II stern drives. Sierra Mercruiser water pump kit For Mercruiser Alpha I Gen II stern drives from s/n D469859 and above 6 blade impeller with key drive Replaces Mercury 817275T4, 817275Q05 Replaces Mallory 9-48315