Caburettors are designed to retain some fuel in the fuel bowl, even if the fuel is switched off and the engine run until it cuts out, there will still be a little fuel left in the carburettor.
When fuel is left for any period of time, especially 2 stroke mix, the fuel will degrade and leave deposits in the carburettor, carbs rely on being clean and having the correct size orifices to function correctly.
After a period of no use, if your outboard is difficult to start, idles poorly (or needs the choke slightly open to run) or is either hesitant to accelerate or lacking in power, amongst other possible causes there is a likelihood that your carburettor is dirty.
The pictures below are a set of nozzles / jets from a common carburettor as received which obviously had some running problems and then the same set of nozzles / jets after a bit of TLC
As you can see there is a huge difference and after a good clean up the engine ran just fine.
Avoid this happening to you by keeping clean fresh fuel in your outboard and draining it down properly prior to any storage periods