Looks like an engine
siphon break. If so you could run a small diameter tube from the top of it discharging into the cockpit
to act as a telltale to check the cooling water
is working as well working as a siphon breaker.
I used a needle valve at the top of the vented loop and a copper tube. If the normal flow rate slows, I screw the valve in and back open which breaks up the salt