If you had something detectible by soap bubbles, you'd be noticing soot, like black dust particles, slowly building up on surfaces in one engine room and not the other. However, that usually means a leak in a direct connection, turbo clamp, etc. Because much of your exhaust is water jacketed, you may get leaks between the water jacket and the exhaust pipe that would not show up with soap on the outside or soot in the ER.
I believe many of the monel pitting problems mentioned were discovered when a monel water jacket started leaking cooling water to the outside of the pipe, not to the exhaust on the inside. In that case, people have seen it oozing and then dripping.
Doug Shuman
