Mercury 30 hp 2 cylinder 2 stroke Ignition Trigger Position

[JDusza]

I'm helping a friend with their 30 hp Merc 2 stroke. Upon throttle up the engine sounds like it is choked up but carburetor adjustment doesn't yield the results we want. It continues this way at high throttle. I peeked under the flywheel and saw that the ignition trigger does not have an adjustment and is not tied to the throttle linkage on this engine. So, how is timing set or improved on this engine?
Thanks,
J