I ran out of fuel using my outboard engine the other day, when I had checked the tank beforehand and thought I saw plenty of fuel. I had forgotten to open the choke for twenty minutes or so. My question is, does leaving the choke closed increase fuel consumption so much that I could empty a tank much quicker than normal?
It absolutely does use more fuel. What the choke does is creates a restriction in the carburetor, which in turn creates a higher vacuum so the engine will draw more fuel when it is cold. This is called fuel enrichment. It allows the engine to warm up and keep running, but at the expense of using more fuel to make it happen. When leaving the choke on for a longer than needed period of time, the engine will consume a lot more fuel than it otherwise would. It also kills the performance of the engine as well, because the engine will not be allowed to draw as much air as it would normally be able to in higher RPM situations.