The vented loop is only required if the generator exhaust elbow is below the waterline of the boat. It should be installed in the hose that goes from where the cooling water leaves the block of the engine to the exhaust elbow. So this is after the pump and engine cooling system. So it would be on the pressure side of the pump rather than the suction side. The fact that there is slight bit of water escaping when the engine is started shows that the valve is working. >From your description of the plumbing system it looks like the vent is installed in the wrong place. Charles Field 561-255-2561

My generator's installation instructions call for an above-water exhaust and a vented loop if the top of the exhaust mixer is less than 10 inches above the waterline. Rich Gano Frolic (2005 Mainship 30 Pilot II) Panama City area Subject: T&T: Vented Loop Usage The vented loop is only required if the generator exhaust elbow is below the waterline of the boat.