I have an old 24 ft cabin crusier with a 302 Ford Engine. Recently removed the engine and rebuilt it. While it's out of the boat, I am cleaning, and learning about the boat. On the engine, where the fuel line connects, there is a solenoid, (I think that's what it is) that has wired coming out and a tube with a hose connector on it. I followed the hose, and it goes all the way to the middle of the boat, where it connects to a tee, the tee is connected to a gas cylinder? Looks like a propane tank, then goes from there up under the control panel near the Tach. The gas cylinder says it is Auto Emission Analyzer Gas. Why would this be tucked way up under the cabin? Does anyone know why this would be on my boat?