Hose from Strainer Piping to Shaft Coupling

[Pritch6397]

I was filling the engine fresh water strainer while the boat was on the hard and the seacock was closed I noticed that the water kept draining out. I then noticed that water was running out around the prop seal on the exterior. I then found there is a hose from the under side of the strainer piping to the shaft coupling that would allow the water to drain to the coupling and out around the prop shaft. I am just curious what the point of this hose is when obviously water can fill the coupling from the exterior around the shaft?

 

[Jared Dunning]

Its to keep the shaft bearings cool while running the boat.