Good plumbing question on a 47
 

I'll post picture a little later... but here's the question.

while I took both back engines from the the bilge, there is a big,( 1 1/2 or 2 iches) water inlet in the flat part of the notched transom, just before the transom of course. this inlet is directly connected to a ball valve. I thought at the beginning, it was either for gen cooling, or engine cooling, or, or, or... it end up this water hose, plumbed in this water inlet, goes DIRECTLY AND STRAIGHT to the port side of the hull, hooked directly to a water outlet, just like a bilge pump is plumbed. So this inlet, does not, in anyway, bring water to any device inside the boat...

What is the logic of this? brings air from the side outlet, down below the hull?

anyone one can find a good answer to this? when I post picture, see the brass ball valve at bottom and follow the hose up to the top side...

It vents the notch or transom mine has the same thing , to release vacuum on the hull when getting on plane , like having a 5 gal pale upside down in the water and trying to pull it up ! vacuum !!

that is something I was thinking about... but though it was made too simple to be true, or efficient...

Here's the picture !

MIne just dead ends high up inside the transom .

what's the purpose of the hose on a number 6 drive? vacuum also?