Is it possible to rotate a fan by splitting the phases by 100 degrees?
Where a motor is designed to use 90 degrees phase shift between main and aux windings, that phase shift will result in the maximum starting torque. 

Any phase shift will result in some torque. The cosine of the phase shift would be a good approximation to the resultant torque, so if 90 degrees was 100%, even 120 degrees would be 86% of maximum.