Recently replaced my pump and motor,.Installed myself. We have a small pool built in 85 with an attached above grd spa. Before purchasing I looked all over the existing motor as we'll as on the impeller for any identification as to what the hp was but all the labeling was long gone. Researched online and decided on a direct replacement Whisperflow single speed and went with 1hp. It all went together with no problems with the exception that I now have a lot of cavitation in the pump basket.I checked for suction leaks and their are none. Plumbing is 1 & 1/2" except for a short 8" piece of 2" pvc going into the suction inlet with a union. Some online articles on cavitation state that if going to a smaller impeller doesn't solve the issue it's possible that my original motor was 3/4hp and replacing it with the 1hp is what caused the issue. To save $$ i've always taken care of the pool and equipment myself and I'm no expert but know that a too powerful pump will create more resistance to flow, pulling more water than the pipes can supply, which ultimately starves the pump and causes cavitation. On recommendations I have replaced the 1hp impeller with a smaller 1/2 hp impeller but nothing has changed. Don't want to have to buy another motor but if I have to downsize to a 3/4hp it may be my only alternative.
Looking for input from those that have dealt with this issue. Any feedback much appreciated.