150 hp Yamaha slow idle problem?

i have a 1998 19’ sea pro with a 1998 150 hp 2 stroke Yamaha. boat runs great but when i go to slow idle thru no wake zones or thru traffic or congested areas the engine seems to sputter and want to turn off. i usually have to go to neutral and fast idle to keep it idling. have new plugs and water / fuel separater to install this afternoon. any more advice or recommendations.
19’SEA PRO CC//150 HP YAMAHA
SAKATUMI TRAE

never hurts to do a carbon treatment (seafoam)

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