yamaha 90HP

[chompin]

the engine is increasing and redusing and decreasung speed on idle mode and some time even will shutdown and will not keep idle speed at all

[smokey]

That sounds like a pin hole in the fuel pump diaphragm.

[Ken]

Noam,
Could be clogged low speed jets in carbs - try a shock treatment with SeaFoam or RingFree.
Good luck [img]smile.gif[/img] ,
Ken K

[chompin]

thank's
i think it is an electrical problem could it be the ignition coil or the electrical brain ??

[jb123]

if it is easier for you to replace costly electrical parts than clean out your carbs, please let us know what it was that indeed did fix your motor, as we all learn by that.

[chompin]

i try to clean the carb's again but nothing .
the engine run ok and suddenly decide to back fire and stop, would not respond to half throttle , when i crank it and immediately push full throttle before the engine stops he would leap and suddenly run ok with high rpm
and the problem returns as i describe .

i think the bast thing to do is to paint it blue
and toss it to the ocean

[chompin]

i torn the carbs apart
all jets and plugs and clean .
it didn't solve the problem.
can i assume it is electrical problem ?