Jacuzzi Magnum Pump Leaks

I bought a house with an indoor pool that has a Jacuzzi Magnum 1.5 hp pump.  The pump leaks.  I have changed all of the seals and o rings and it still leaks.  The leak appears to be coming from the large o ring that is on the motor and goes inside the housing with the large lock ring to secure it.  I have the o ring lubed and put lube on the inside of the housing.

Correct me if I’m wrong, but that o ring is the only way to keep the entire pump from leaking at that location.

Any thoughts