Mercury Mariner V-250 V-275 Outboard Service Shop Manual 1990, Page 268Get this manual
7Install LOWER gasket8Install water pump alignment pins(Obtain alignment pins locally 9Install plate and UPPER gasket onto alignment pins ACAUTION
A visual inspection of impeller drive key MUST BE made to determine that drive key is on flat of drive shaft after Impeller is InstalledIf key has moved off flat of drive shaft, repeat steps 10 and 11 IMPORTANT: When performing gear housing repair that requires removal of water pump impeller, it is rec ommended that the impeller be replaced If old impeller must be reused, DO NOT install in reverse to original rotation or premature failure will occurOriginal rotation Is clockwise
aWater Pump Alignment Pins (OBTAIN LOCALLY) -Upper GasketPlateLower GasketSealing Ring Goes UP