Could be a few things, but likely carb problem. You can get a Factory service manual from any Nissan/Tohatsu dealer.
Draining the carb after running it down is a better way to go than just running it until it stalls. If not drained... then if you store the motor on its side, the remaining fuel can be right where you don't want it when it evaporates into varnish crud. On your carb, the drain screw is super-easy to access, and draining that last teaspoon should take you maybe 20 seconds -- including removing the cowl from the motor. At our dealership, we recommend carb draining if the motor will sit for a couple of weeks, even during the season.
Spraying "carb cleaner" down the throat makes the choke and throttle plates shiny, but does nothing whatsoever for cleaning the carb internals. Only removal, disassembly, and proper soak cleaning will effectively address internal varnishing.