I have always heard these devices referred to as "water-lift mufflers" or "lift mufflers" which is what the company that made our custom fiberglass ones called them as does our diesel shop. A friend who had a pair of horizontal units installed in his converted steel fireboat to quiet the 8V-71 Detroits called them "mufflers." If you look at the website of National Marine Exhaust in Marysville, Washington, one of the top exhaust fabricators in the country, you'll see they use the term "riser cans" and "wet or dry mufflers." Nothing I saw referring to "silencers." But I suppose you can call them whatever you want as long as the person you're talking to knows what you mean. ______________________________ C. Marin Faure GB36-403 "La Perouse" Bellingham, Washington