1985 OMC 65, 100 and 155 HP Models Commercial Service Manual, PN 507450-D, Page 104Get this manual
If there is any question that an anti-siphon valve is suitable, then the following test should be made using clear transparent hose Remove anti-siphon valve from tank and install fittings and hose Water must not
Fill hose with water to height of 500 mm (20") run from valveAn occasional drop is acceptableA continuous drip is not acceptable