Weird particulate in engine

[davidlorean]

I just cleaned the carb on my Briggs (8.75 gross torque 190cc Professional series) engine and noticed a bunch of gunk between the carb and the valves. This lawnmower engine is used in a hovercraft to turn a fan that pushes air down under the hull of the hovercraft. I hover it on the San Francisco Bay, and there is a lot of saltwater spraying around all the time, so I assumed all that build-up was salt. And since I'm smart and care about my health, I tasted it. It did not taste like salt. It tasted a little bit like gasoline. I've noticed a little bit of this stuff in the past, but it looks like a lot this time. And the part of the valve looks rusted. Any idea what might be going on here? Could it be from the ethanol in the fuel (I use premium 91 octane gas in california, which I think is 6 or 10% ethanol). Is this a big enough of a deal that I need to clean it out and fix the problem before using it again? Thanks!