5239216 Spa Pump 230v 16A 56f 2-Spd 3.7/3.1" threads

5239216-S Spa Pump 230 Volt 16.4 amps 56 Frame 2-Speed, 3.7/3.1" threaded connections, 10-5239216-K.

Note that this rare model has a BIG 3.7" outside diameter thread on the intake, and a normal 3.1" thread on the discharge.

And if not available, you can use 5235216 with a threaded adapter here:

5235216 and Thread Adapter

Can be single capacitor design, or dual capacitor, sometimes ships with big 6 slot base under the motor, and sometimes with 4 slot base, depending on availability.