There is usually a line in the afternoon at the coin-operated wash rack where I launch my boat, so it really bugs me when the guy ahead of me takes a long time. I wait patiently as he soaps up the whole boat, washes it, then rinses the boat and trailer, and then, when he's done, he puts a second or even third set of coins in to flush the engine. To save time and get the most out of the limited water, I wash and rinse the boat and trailer at the same time as I flush the engine. I simply use two hoses and a simple Y fitting, available at a hardware store or garden center. I hook up the Y and run one hose to flush the engine and use one to wash the salt off the boat and trailer. The Y fitting I use is brass (plastic ones break too easily) and has a valve for each hose so I can make sure the engine is getting enough water.