2001 Edition Yamaha F225A and LF225A Outboards Service Manual, Page 95Get this manual
Throttle control 25Check that there is no clearance between the port and starboard throttle stop screws and 8, and the throttle body levers and 9If there is any clearance, repeat step 24
26Start the engine, and when the engine speed is at idle, check the average vacuum difference between the port and starboard banksAdjust if out of specificationAverage vacuum difference between port and starboard banks: 40 mmHg (53 mbar, 1.57 inHg)