The impeller sources are drying up fast. Might be a good idea to keep your old impeller core with a label on it with Mercury Impeller part# 47-24447 and a few measurements from the new one in case you have to have one custom made in the future.
You can use the instruction manual for the WD-4S motor to get an idea of how to start and run your motor. They use the same impeller and have similar lower gear boxes. The gear tooth numbers are different in the 6hp motors if I recall correctly. Use modern outboard or two cycle oil and you can thin the gas/oil mixture to 24:1 or 32:1 in order not to leave a rainbow oil slick behind the boat.