The Pinnacle is actually an uprated pump so it is really a 1 hp pump. There is a numbers game that all pump manufacturers play with pumps. There are full rated pumps and uprated pumps. They take the HP rating of the motor and multiply it by a service factor number to get the brake HP. Brake HP is the actual HP rating of the pump. The service factor is really how much power is left under an extreme load. Uprated pumps have a lower service factor than full rated pumps For example. a fullrated 1.0 hp pump has a motor HP rating of 1 and a service factor of 1.65. When this is multiplied you have a brake HP of 1.65. An uprated 1.5 HP pump will have a HP rating of 1.5 and a service factor of 1.1. Multiply these and you also get 1.65 brake HP! If these two pumps are in the same manufacuturer's model line they are exactly the same pump with the same impeller, volute motor, etc. The only difference is the numbers written on the pump and possibly the price! They are both 1 hp pumps! One is just rated more conservatively (and IMHO, accurately) than the other! The Pinnacle line are all uprated. Your model has a HP rating of 1.5 and a service factor of 1.1 for a brake HP of 1.65! I would not recommend replacing the motor with a dual speed one. It will cost you almost as much as a new pump would and the pump might not perform properly at low speed since the impeller and volute were not designed to run that way. All pump motors are made by AO Smith, btw!