Hang on, Hang on. It may not be too much. Gimme the model number, so we can determine the year. If it is old enough, it should be 24:1, in which case 50:1 will still make it smoke, and not because it is burning oil, but because it is burning piston.
Now, mind you, they (6 hp OMCs) were most common in the 70s, however they still were made beforehand, so he could indeed have a pre '64 motor, which is made to be run on 24:1. Also, myself, and a few others prefer to run some of the 6 and under motors from the changeover period in '64 until about '70 with 24:1, as they still used bronze sleeve bearings in certain parts of certain smaller motors.
Go ahead and tell us the model number. Only way to be safe.