Reason for choking an outboard?

The reason for a choke is to enrich the fuel mixture while the engine is cold - just as in a car. Cars are pretty much all fuel injection now so use the engine management unit to do this instead. Some outboards are still carburettor fitted - especially the smaller ones - so they need a choke. You should only need it for a short time once the engine has started from cold - just slowly push it in and see if the engine runs ok.

You may also need it even if the engine has only been stopped for a few minutes, you'd be surprised how quickly they cool off (after all, no big bodywork around them to keep them warm) - but you may only need half-choke (pull it out a bit!).

Hope this helps

You are choking the air supply off in order to get the engine vacuum to bring fuel up into the engine. You don't need it long, only a few seconds. Some motors now have auto choke/enrichener that will do all that for you. Some even with have primers that squirt fuel into the intake so no need for a choke.

Yeah, you have two good answers already.

You are trying to make the fuel mix rich to help the cold engine start.

Feather the choke until you hear the engine clean up. Could be seconds or maybe more for a cold blooded engine.