1983 Yamaha 30EN Outboards Service Manual, Page 65Get this manual
Drainless mechanism The lower bearing is connected to the upper bearing by rubber tubeDisconnect the tube on the upper bearing sideWith its open end in your mouth, breathe in and outWhen breathing in, the valve should close and no air flowsWhen breathing out, the valve should open, allowing air to flowTherefore, if air flows when you inhale, the valve is faulty and should be replaced Check valve replacement 1Pull out the check valve using pliers