Fastest, easiest carb clean. Johnson 70hp 1980s

Old fuel will evaporate over winter and thick oil and varnish will be left behind. Gravity will pull this into the bottom jet as it is the lowest point of the carburetor. 99% issues with these engines are caused by this.
To prevent your floats from cloging with oil etc over winter you should disconnect your main fuel line while you flush your engine after its last use. This will empty the fuel lines to your fuel pump and up to your carburetors. I don't recommend running your engine out of fuel as different carbs may run out at different times. If one cylinder stops getting fuel while the others keep the engine ticking over you won't be getting oil to the cylinder with the dry carb. Just run the engine for a few seconds to clear the lines up to your carburetors then shut the engine off and drain the carbs from the drain plugs.