2001 Edition Yamaha F225A and LF225A Outboards Service Manual, Page 93Get this manual
Throttle control 15Tighten the synchronizing screw of cylinder #4, and stop tightening when the throttle plate starts to moveSimilarly, tighten and adjust the synchronizing screw of cylinder #616Tighten the port throttle stop screw until it contacts the throttle body lever 9, and then turn it one additional turn
Carburetor synchronizer: YU-08030