1976 Johnson 4HP 4R76, 4W76 Outboards Service Manual, Page 49Get this manual
WATER PUMP SERVICE CONT'DeObserve location of keyway in impeller and key in driveshaftSlide water pump assembly down driveshaft and engage keyImpeller housing cover will contact spacer in water pump cavity before cover flange contacts face of gearcase leaving space of about .010"See Figure 6-7BSlight finger pressure will seat cover on face of gearcaseThis fit is necessary for proper operation of the water pumpAttach pump to gear case with screws dipped in OMC Gasket Sealing CompoundTorque to specificationsfReassemble gearcase to exhaust housing as described in ''Reassembly of Gearcase to Exhaust Housing
cWhile holding driveshaft down in gear case, slide impeller housing and impeller off of driveshaftRemove key and slide impeller plate off of driveshaftRemove and discard water tube grommet from impeller housingdInspect and replace components as necessaryeApply small bead of OMC Adhesive "M" beneath impeller plate and install on gearcaseInstall impeller pin in driveshaftSlide impeller down driveshaft and engage impeller pinLubricate impeller with oil and install impeller housingRotate driveshaft in clockwise direction while slipping pump housing over impeller to position blades correctlyAttach pump housing to gear case with screws dipped in OMC Gasket Sealing Compound and torque to specificationsfInstall new "0" ring on driveshaft