Dumb question:
Have you taken a flashlight, looked into the stern's exhaust outlet, and check for any obstructions?
My guess if that looks fine, a partially clogged exhaust water box (muffler) or resonator.
Have you taken a flashlight, looked into the stern's exhaust outlet, and check for any obstructions?
My guess if that looks fine, a partially clogged exhaust water box (muffler) or resonator.