will not start without giving more throttle

[upperwater]

2006 yamaha 150 4 stroke , 600 hrs , used ring free and gas stabilizer every gas fill. All motor gas filters and vst done 3 yrs ago for maintenance, runs great , no hiccups, but last time out , it didnt want to start unless i used the throttle handle to put in neutral and give it a little more gas on the throttle, not every time. Any ideas, maybe some bad gas i got. Allaays traileded so i get at gas stations, not at marinias , i did change water fuel separtor, looked good

[TownsendsFJR1300]

When it does start COLD, does it idle slightly higher(as it should COLD), then the idle drop down?

[99yam40]

the ISC valve is suppose to open to 100% when you shut down the motor so it is ready for the next start up.
you should be able to hear it clicking after you turn off the key, do you hear it each and every time?