I am having my risers/elbows replaced on my 2002 4.3 L MPI Mercruisers. Between the engine elbows and the exhaust tube one of the clam shell valves ( not sure of technical name )that prevent backwater from entering the engine had corroded and came loose. It was retreived in the exhaust tube. This is a salt water boat and the guy who is working with me suggests that I remove the remaing ones as thee are prone to problems and have no real function except in the most extreme circumstances. Any thoughts pros or cons about removing them?
