did you clean the carb? or the motor? it could be the idle screw turn it in 1/8 of a turn and wait for the motor to respond before you turn it again or you have dirty jet in the carb clean it
Are you using fresh gas? When I started my 2003 8hp 4stroke the first time this year I used old gas and it would not idle properly, then switched to fresh gas and it idled perfectly.