Pool has been in use for several years with no problems of this nature. It is my son's, so I have not been much involved with it till now.

Yes current is being measured with an amprobe. The original motor failed, not sure how, a brand new 3/4 hp motor drew too much current so it was returned and now a slightly used 3/4 hp identical motor (A. O. Smith USQ 1072) is drawing over 7 vs. 5.9 nameplate and after a while the cutout operates. It eventually resets and it the cycle starts over. Current draw with no load (strainer open to the atmosphere) is less than 4 amps.

A new pressure gauge indicates 8 psi at the filter, so I believe we can rule out the return lines.

It must be the suction lines although hard to believe as there are two all the way to the pump, one from the two main drains and one from the two skimmers. The suction Y valve at the pump has been disassembled and is OK. We will try backflowing the suctions lines and see what happens. Thanks for the help. PMD