1989 Johnson Evinrude "CE" 9.9 thru 30 Service Manual, P/N 507754, Page 67Get this manual
4Point end of fuel hose into container below top of tankDepress the ball in the fuel connector until any remaining fuel is expelled5Add air to bring pressure back to 10 psi (69 kPa)6Submerge fuel tank in water, one portion at time, in the same manner you would check tire for air leaksAny air bubbles indicate leak point which must be repaired or replaced7After testing, release tank pressure through valve stem before removing capDo not attempt to remove screw from center of Test Adaptor PIN 389945 32C