1978 Johnson 175, 200, 235 HP Outboard Service Manual, Page 135Get this manual
GEARCASE PRESSUREVACUUM TESTS To test gearcase sealing, proceed as follows: 1Remove drain plug and screw in pressure test gaugeSee Figure 6-109Stevens Experimental pressure test gauge illustrated2Pump pressure up to 3-6 psi (21-42 kPa)If pressure gauge indicates leakage, submerge gearcase in water to determine source of leakage as evidenced by bubblesIf gearcase pressure gauge does not indicate leakage, increase 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 test3Screw 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 Chart1Oil level plug 6 512