Initial setting 1 turn open from closed for both needles. That should allow motor to start and run. Adjust from there when motor is warm under a load (as in running on boat at speed on water) Make small changes in Hi speed needle to arrive at at the point between too rich and too lean where motor runs best...make small adjustment and let motor run a bit...too rich...motor slows too lean and motor sneezes...back off toward rich and see if tht is ok. Tillotson MD or MT carburetor...turn out to richer turn in to lean...usually.
Then set low speed needle for best idle.
There is more to it but essentially that is small engine carburetor adjustment.
Louis