yamaha four stroke f80 cold idle

hi all ,
I have a F80 outboard 2002 fourstroke which has been regularly serviced
and has got the following problem before i call in a yamaha specialist
does any body have a "home fix"?
The problem i have is the engine is left on average 2-3 weeks unsued ,
when i start it it from cold it fires ok but runs like it is "missing"
or on three cyls or something? also i cant lift the throttle lever
because this stalls the engine however if i leave it running for 2/3
mins stop it then re start it 9 out of ten time my problem is solved
and it runs perfectly all day , i always pump the primer bulb and open
the air vent on my tank and my petrol is not stale? is there any thing
i can do myself

thanks for listening
stu the codfather