1971 Johnson 4HP Outboard Motors Service Manual, Page 48Get this manual
SCREEN COVER GEARCASE HEAD OILHOLE RIVET'
OIL RETAlNER PLUG AND WASHER
CLEANING, INSPECTION, AND REPAIR
Wash parts in clean solvent such as Solvasol and dry with compressed airDiscard gaskets, seals, and rings, as new ones should used during reassemblyCheck f1atness of gasket surfaces as described in Section 5, Power HeadRemove dried cement and particles of gasket with trichlorethyleneCheck parallelism of machined faces of exhaust housing and gearcase extension, if used, surface plate, using surface gage and scriber or dial indicatorSee Figure 6-8drill press table with spindle locked to top of housing can also usedDO NOT attempt to straighten bent housing; replace itInspect propeller shaft assembly, pinion gearand driveshaft splines for wearbent exhaust housing will cause excessive crankshaft spline weardInspect bushings and thrust bearingInspect impeller for wear or deteriorationCheck impeller pin driveshaftInspect impeller housing and plate for scoring which reduces water output