Nissan 6HP Longshaft Outboard Quits when shifting out of neutral

I purchased this outboard in 2011 (brand new) and it has worked like a champ until tonight. We pull out of the slip and exit the harbor just fine (about a 5 minute ride) and the motor just shuts down. It took an uncharacteristically large number of pulls to start her again, and she did so only reluctantly at first and then all of a sudden it seems like the engine was able to run at high rpm in neutral but would inevitably stall with an occasional "timing is off" kind of sound, almost like a mini backfire. Also, when running in neutral and shifting into forward or reverse, the engine would immediately stall. I am baffled. Help please!

You did not mention model (year is irrelevant). Assuming you have an NSF6B or C, and are running with external tank and primer hose. Of course, if the tank vent is closed, you will run out of gas (goes without saying). Odds are the carb has varnishing. If you are not running the next day, you must empty the carb every day you do run, either by idling the carb out (takes maybe 5 minutes on these), or by using the drain screw. Otherwise, as the fuel evaporates, it leaves a residue in the tiny passages. If running with internal tank, it needs to be nearly full when first starting, in order to assure fuel is delivered to the pump.