Mercury Mariner V-250 V-275 Outboard Service Shop Manual 1990, Page 186Get this manual
Water Pump REMOVAL and DISASSEMBLY IMPORTANT: It is recommended that all seals and gaskets be replaced (as normal repair procedure) to assure effective repair1Remove guide and seal2Remove bolts and bushings
4Remove impeller from drive shaft (It may be necessary to use punch and hammer to drive impeller upward on drive shaft In extreme cases, it may be necessary to split hub of impeller using hammer and chiseL) 5Remove impeller drive keyaImpellerDrive Key