On mine, there was (as I recall) a sort of oblong plastic plug, with what looked like a black rubber grommet. It was, oh, six or eight inches from the rear of the motor. The grommet was the telltale exhaust.
Pull the cowl, and look for a rubber (or plastic) tube going to that area, and not obviously meant for anything else. That'll be it.
Of course, Honda may have changed the location of the telltale as well. If I still had mine, it would be going on ten or twelve years now.
Should also add that you can pull either end of that tube and run the motor to see if it or the outlet piece is plugged. Less mess if you use fresh water when doing that, though.