That key switch panel is also used for motors down to a 25hp. Most of the older ones below 115HP had chokes.
First check to be sure that you squeeze bulb is hard before you start. It sounds like there may be an issue with it not getting enough fuel at start up. You might just have a faulty squeeze bulb.
Another thing you might do is drain the fuel from you vapor separator into a glass jar and see what it looks like.
When was the last time that you changed your high pressure fuel filter (in the vapor separator)?
One last thing to try...and there are many....when you go to start the motor, turn the key switch to on, listen for the two second beeps and after that two seconds (during which time the high pressure pump is pressurizing the system)....then turn the key to start.
If all that checks out and does not help...then it will be time to check a few other things like Idle Air Control, etc. Let's save that for later.
Mike