pompebled

That's the one that requires some 15mph hull speed to get the flow going and will only work in combination with a sucktion outlet when running at lower speeds.
When you putter around without making a fast pass, the flow will most likely not get going at all, due to air in the system.
Inlet #1 and 2 may have slightly more drag, but will provide cooling water at low speed aswel.

Regards, Jan.