system installed in the 70's and 80's. They sounded like tractors when started up. I replaced mine with an off the shelf injection elbow and a Vetus "L Plastic waterlock" muffler and a Vetus Gooseneck LT50 riser. The gooseneck riser allowed me to get the exhaust high enough to prevent back flow. I have a pretty low free-board boat with the engine well below water level. For the injection water I used Groco Vented loop which I modified to accept a 1/4 inch plastic tube that I directed directly into my cockpit locker drain. That way I don't have to worry about the valve getting clogged and causing a failure which floods the engine. By looking into the cockpit drain I can also see that water is flowing into the system thereby checking the pump output. A 1/4 inch tube doesn't pee enough water to effect the operation of the exhaust system. If you want to really quiet down your engine noise install a Vetus DEMPMP50 resonator/muffler. I installed one on my generator and the difference in noise level was astounding. Someone mentioned the Centek units and I agree. If you can get one to fit then I would go with them as well. I used one on my generator and I'm very happy with it. I'm not sure that Centek has a goosneck riser like the LT50 but you could mix and match if it came down to it, I did on my generator.