1995 Mariner Mercury Outboards Service Manual 50HP 4-Stroke, Page 237Get this manual
2 Install exhaust deflector plate, if removed
IMPORTANT: If impeller being installed has been previously used and vanes have taken "set," DO NOT INSTALL THE IMPELLER WITH THE VANES REVERSED FROM THEIR PREVIOUS "SET" AS VANE BREAKAGE WILL OCCUR SHORTLY AFTER UNIT IS RETURNED TO SERVICEInstall impeller and nylon washeraSeal CarrierExhaust Deflector
Install base gasket, base plate, pump cover gasket (NEOPRENE STRIP FACES UP), nylon washer and impeller key