Look for a large screw at the left(?) rear of the leg, up at the top just under the lower cover. It looks like the drain/vent screws for the gearcase. If you have one, you can unscrew it to see if water is being pumped -- will shoot out a couple of feet if working properly. This is the source of cooling water for the engine, so after briefly checking shut off the motor and reinsert the screw before firing it up again.
The carb has an idle mix adjustment at the top (fixed h.s. jet at the bottom). Initial idle setting is 1 1/2 turns open (counterclockwise) from lightly seated. The motor should run at this setting, subject to further fine tuning when warmed up.
