Now that it is a closed body of water, your strategy of using a system of push/pull spawners is likely to work. Or, seal all sides of the 'ocean' making it in effect a huge lake. You may have to create a subtle sloping gradient of the sea floor from the source end to the exit point. Seal the map edge at the source point and place your spawner there. Instead of an ocean, make it a very broad river channel. Or at least not one that would be observable. Not only that, whatever the producing spawner creates, will simple drain off the edge of the map, while the drain spawner will simply draw more water in from the edge of the map, meaning that there won't be a current between the two spawners.

The water spawners you're trying to use to create an artificial push/pull effect will not be able to compete with the volume of water in the ocean. A river flowing into it will produce a little current and may move towards the edge of the map if it is strong enough. The ocean is a static body of water that is filled from the outside map boundaries.

Creating map water in cities skylines