Be VERY careful of fire when this happens. The very same thing happened to me with an old vintage 3hp Johnson. Fuel sloshed out on the cowl during this episode and I thought it was wiped clean. Just enough went down in the cracks to ignite when I started the motor. It flashed up and I actually unscrewed the motor and dunked it in the water to stop the flames. This was on a ply skiff and I had no fire extinguisher aboard. The motor got some "char" marks but otherwise nothing was hurt. This makes a good case for external tanks. Bill