At reduced RPM, Yamaha’s labyrinth exhaust method minimizes the engine sound. F9.9 features a h2o-sealed outer wall around the exhaust muffler. It helps lessen the exhaust sounds levels for the tranquil operation. https://minalluf433570.theisblog.com/34985896/the-smart-trick-of-9-9-outboard-yamaha-that-no-one-is-discussing