1979 Evinrude 4 HP Outboards Service Manual, PN 5424, Page 68Get this manual
eObserve location of keyway in impeller and key in driveshaftSlide water pump assembly down driveshaft and engage key Impeller housing cover will contact spacer in water pump cavity before cover flange contacts face of gearcase leaving space of about 0.010" (0.25 mm) See Figure 6-9Slight finger pressure will seat cover on face of gearcaseThis fit is necessary for proper operation of the water pumpAttach pump to gearcase with screws dipped in OMC Gasket Sealing CompoundTorque to specifications
1Water tube grommet 2Screws 3Impeller housing cover 4Impeller plate 5Impeller 6Impeller drive key 7Impeller housing cup 8Spacer
1About 0.010" (0.25 mm) press to gearcase face
Figure 6-9Correct Water Pump Assembly to Gearcase