OK, here it is, 44.1(b):
"if the boat caused injury or serious damage or gained a significant advantage in the race or series by her breach her penalty shall be to retire."

So, if you push yourself around the mark, and as a result beat three boats around the mark; rather than pushing yourself behind the mark, which would cause you to be behind those three boats, you're gaining a significant advantage (depends somewhat on the size of the fleet).

Propulsion may be a stretch, but 44.1(b) is not. Fair sailing rules may also be applied.

As for why we're having the discussion, if it's a drifter, the race may be abandoned, but doesn't have to be (think distance race), so this could very well be a real issue at some time in your sailing career.

Hope this helps.

Mike