MerCruiser Pre-Alpha Water Pump Housing Kit by SierraFor #1/R Units without flush S/N 2763442 - 6854392 Pre-Alpha MerCruiser Drives. Models which have been retro fitted with an Alpha style (no preload pin on top of driveshaft) must use Kit # 18-3320.Kit Includes: 18-3109 - Water Tube; 18-3017 - Impeller; 18-3116 - Housing; 18-2919 - Water Pump Base to Gear Housing Gasket; 18-3417 - Water Pump Base; 18-3110 - Grommet; 18-2945 - Gear Housing Drain Screw Gasket; 18-2826 - Water Pump Base to Gear Housing Gasket; 18-2914 - Lower Water Pump to Wear Plate Gasket; 18-2915 - Upper Water Pump to Wear Plate Gasket; 18-2944 - Seal Ring; 18-3117 - Plate; 18-7158 - O-Ring; 18-7162 - O-Ring; 18-7173 - O-Ring; 18-7176 - O-Ring; 18-2801 - Water Pump Gasket; 18-7196 - O-Ring; 18-7426 - O-Ring; 18-2919 - Water Pump Gasket;