yamaha 90 hp halted

[chompin]

the engine seems to run fine and suddenly starts
to backfire and stops, then he will hardly start and would run leap even on full throttle after while he breach and runs ok it happens every time.
i try to chek the parameters when it happens and:

1. there is a spark on the plugs .
2. there is a good fuel supply from the pump .
3. i try to clean the carbs a few tims .

i am having this problem for long time and fail to fix it, what other possibility can i check.

**the fishing season is starting here and i ..... :-(

[boats.net]

It sounds like it is running lean, The low speed jets in carbs are plugged. Need to clean carbs and check syncronization as per the service manual.

[chompin]

i did clean them and it didnt solve the problem , how can i deprived that it is electrical problem ?
is there a repair kit for carbs may ?