I have a Hayward Super II pool pump, A.O. Smith motor, 2 hp, 2 speed model SP1615Z2MC.  It runs fine on low speed, then when going to hi speed it kicks off.  I have replaced top capacitor, not the problem. Do you think its start capacitor or thermal switch?  Do you sell either for this model?  With its age, should I just replace the motor?  Thanks in advance for any help.