I just got my first boat and got it running after sitting 10+ years.  My question regards plumbing.  The water intake hose from the transom to the engine came with 2 (assemblies).  1 is a simple T which I used to provide water to get engine running.  The other replaces the water inlet with a valve.  I will assume that this is used when boat goes in water so what is the technique used with the valve?  Thanks for your help, don't want to blow things up by not asking questions first.  No ego here...