1990 Johnson Evinrude "ES" 60 thru 70 Service Manual, P/N 507873, Page 66Get this manual
6If you suspect the anti -siphon valve, perform these tests Remove anti-siphon valve from fuel tank and install adaptors and clear hose as shown Fill clear hose with water until "X" dimension is 20 in(500 mm)Water must not run through valve Increase water level until "X" dimension is 25 in (630 mm)Water must begin to run through valve before reaching 25 in(630 mm) Replace the anti-siphon valve if your test results varyTransparent -Hose)-
Anti Siphon_