1978 Johnson 4HP outboards Service Manual, Page 76Get this manual
pressure to 16-18 psi (110-124 kPa)If pressure does not hold, submerge gearcase in water and check for source of leakageMake necessary repairs and repeat testcScrew in vacuum testerPump out to 3"-5" of mercury and see if vacuum holdsThen pump out to 15" of mercury and checkIf gearcase fails to hold on either test, put oil around suspected sealIf leak then stops or oil is drawn in, that seal is defectiveWhen gearcase checks out OK, refill with lubricantSee Section Lubrication ChartReassemble propeller slip clutch without lubricantApply light film of OMC Anti-Corrosion Lube to the propeller shaft and install the propeller, using new drive and cotter pins Figure 6-18), and install exhaust housing assembly in swivel bracketcApply bead of OMC Adhesive "M" to surfaces of swivel bracketSee Figure 6-18Dip swivel bracket attaching screws in OMC Gasket Sealing Compound and install aft half of swivel bracketTighten screws to specified torque
REASSEMBLY OF GEARCASE TO EXHAUST HOUSING
aAttach gearcase extension, if used, to exhaust housing with screws dipped in OMC Gasket Sealing Compound Tighten to specified torque