Since the engine
is probably new, I'm assuming the stern drive is new too. The bravo 2 comes with its own cooling
water connections for the raw water pump
. Normally those are the only cooling connections for the engine
.. I'm guessing the thruhull and strainer was for the old engine / outdrive.
I think it was done that way with the bravo 2 to insure water delivery
to the engine when on plane. I'm betting (I bet a lot is seems) the stern drive has slots/strainer in the stern drive water pickup.
Me I might repipe the Bravo 2 connection to the inlet side of the strainer. Though check with the engine / stern drive manufacturer first, as the old strainer might not even be needed now.
From a hydraulic standpoint water will always seek the lowest pressure path in a parallel piped system. So the water will always flow via the stern drive, due to the higher pressure drop of the strainer.