I looked at it a little closer. When I take the fitting off the hose
what remains in the hose is the ball bearing which sits on a seat and
the spring which sits on top of the ball sorta like this. (O///////


Now the fitting at the end of the hose slips down over the spring. When
you tighten down the fitting the end of the fitting compresses the
spring and snugs the ball down agains the seat thus sealing off the
opening. The other end of this fitting is barbed so you can fit a piece
of hose over it.

The way I believe it works is like a bleeder hose. When the fitting is
tighened down it prevents the oil from coming out. When you want to
draing the oil you attach your drain hose to the barbed end and run it
out the boat into a container, start the engine and let it warm up, set
the engine at idle, unscrew the fitting in the hose to relieve the
pressure on the ball letting it float off the seat and thus allowing
the oil to be pumped out. According to the manual it should take less
than 60sec to pump the oil out.

Mark