nissan 30 hp misfire

I bought a used Carolina Skiff with a Nissan 30hp 4stroke. I'm not sure what year the motor is, but I think about 2000-2001. It seemed to have a misfire (#2cyl) and it turned out to be a blockage of some kind in the carb. I disassembled all 3 carbs and cleaned them and it ran fine. Well after sitting for several months I wanted to use the boat for the first time this year and again it is running rough. Probably gummed up fuel in the carbs again. Any suggestions on a "quick" fix without taking the carbs off again for cleaning? I'm thinking in the future (since I use the boat infrequently) maybe I should shut off the fuel supply and let the motor just run out of fuel while I flush the saltwater from the engine. Any thoughts?

You are a victim of today's poor fuel. I have seen slow-speed passages clog up slightly in only a couple of weeks or so. Yes, best to run the fuel out if planning on sitting for more than a week or 2.

You can try running with an additive -- an automotive fuel injector cleaner such as Chevron Techron, or a marine supplement such as Sea Foam, but they are likely not going to dissolve the varnishing -- at least not fast enough for me.

If storing for the winter, you can also drain the last teaspoon out by using the drain plugs. That also gets out some of the loose debris that made it past the filter. We always rig 30's with 10-micron water-separating filters, especially the newer fuel-injected models.