That actually looks normal.
To get rid of the excess carbon.
Power Tune by Mercury or Engine Tuner by OMC
Yamaha has it's own product, can't remember the name.
Some say Seafoam works on carbon removal NOT.
You can also do an old mechanics trick, once the motor's hot squirt water in the carb as it runs.
A little at a time.
The Power Tune, follow directions.
Then after that, motor still hot, remove the plugs, tilt motor up and squirt product in the cylinders
and let set for 2-3 days. Turning over every few hours.
This will remove a bunch of carbon.
It will be hard to start after the treatments. Clean the plugs and a quick shot of starting fluid.
