My uncle just purchase this boat. in the pictures below r the waterlines for the exhuast. The waterlines have a valve on the end (after the inlets) that can be opened or closed. His question to me was "do i run the valves closed when running and or slightly cracked?" 

I'm pretty sure you're looking at drains for the jacketed headers.

thats what i thought they were too. Hard to tell in those pictures he sent over. So do u juat ise those drains at the end of the day to bleed the water out?

So he should be running them closed then drain at the end of a trip. Thanks