The primary exhaust outlet is through the propeller, so yes that is normal. There are several exhaust gaskets on the way that should be checked if there is much smoke coming from other areas of the gearcase or midsection.
You can cut down on the smoke by using TCW-3 synthetic oil, by making sure that your thermostats are in good working order, and by servicing the recirculation check valves. An annual de-carbon service will also be a real help.
