I'm changing the water / oil cooler for an adaptor to have an external cooler and accusump.
Is the middle hole (just like the oil filter) the inlet?

On the cooler the oil enters via the bolt and exits round the side... On the filter it enters via the side and exits through the bolt/centre

There are diagrams on pages 2-29 2-30 2-31 of the yan' manual with arrows indicating flow

Worth noting that with an external oil cooler it takes a lot longer for the oil to reach a decent temp.

Thanks.
I know it taker longer but the engine is in a single seater race car.