Waterway 1.75hp / 2hp executive pump impeller - Southwest Spas / Sierra Spas (4hp USA)

The hp rating listed is actual horsepower.
Some manufacturers label pumps with BHP (brake Horsepower) In the case of a Southwest Sierra Spa 2hp pump, they are sometimes labelled 4hp. 
The original design impeller is marked with 4hp in the throat of its suction. This impeller is used in pumps exported to Korea as a 2hp 60Hz pump, also used in Waterway Executive Euro 2hp pumps used on Southwest, Sierra and other USA imported spas. 
This impeller was orignally used on Australian spas with Waterway pumps fitted with smooth Magnetek motors in 99-2000.

Original design dimensions: 13mm vane width x 6 vanes, 115mm diameter. Marked 4hp in suction throat on most but not all.

New design dimensions: 107mm diameter, 15.5mm vane width x 6 vanes - performance is the same as original design.