When I restored my boat I used the old Gils and pressure tested the merc style manifolds and used them. They worked, but I didn't trust them. I had no idea whatsoever how old those manifolds were, and the pipe had an odd weld/bend/angle near the tip, as if they had been modified to fit the boat. They say that is bad. Pipe should go straight through the transom, not be angled except at the main bend. So I did what any reasonable person would do and had custom dry exhaust put on the boat last fall.