2010 15MSH 2 stroke. Bought used with low hours. Stock prop. Fresh 87 octane straight gasoline, 100:1 Yamalube. Starts first pull almost every time. Idles well in and out of gear. Idle speed in gear ~800 RPM. Runs smooth up to ~1100 RPM. Between ~1200 and ~1900 it's rough, almost like one cylinder is misfiring. From ~2000 it evens out again and is smooth up to full throttle at ~5200 RPM light boat. I see no mention of carb adjustments in the factory service manual. I didn't expect this roughness from a Yamaha, is it normal?
