Hydro quip spa pack wired 240v,pump motor century flex 48 lasar 115v. Low speed works ok ,but high speed melts the insulation off of the white and black wires on the pump cord going to the spa pack.Amp rating on the pump motor 16.4 on high 4.4 on low.Could this motor be wrong? I am lost.

If the pump is rated 16.4, what is the amp draw on a amp meter? more than 16.4 would be a problem with the motor. I would check low amp draw too, should not be more than the data plate rating.