1993 Johnson Evinrude "ET" 9.9 thru 30 Service Manual, P/N 508282, Page 66Get 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 replaced1sl 7Disconnect hose from tankWith fuel connector housing submerged, check for leakage from fuel nipple and fuel valve pin Depress vent valve pin to check air vent disc valve for leakage1sl 8After testing, release tank pressure through valve stem before removing cap Isl