Hello there, 

Our family recently moved into a house with an existing hot tub (an old CaliSpa PS-3) and I desparately need advice before my teenage children disown me!

Please see attached phots... is the solution a "split nut" / "split coupling"? Where stocks a good selection?
The pump is an old Franklin Electric 1081 pool motor. Alternatively, I'm not sure if the square part (with four nuts) that attaches to the motor could be replaced with a part that will connect to the white pipe? 

Thanks so much for your help, Paddy Irishman!