2008 Mercruiser 6.2 377 Mag. #1a314659. Fuel economy dropped from 2.5 MPG to 1.8 MPG, instantly while up top and running 3600 RPM. The power loss felt about the same as trimming the motor back down, and the engine sounded like it loaded up a bit. New fuel filters, new plugs, new plugwires, new...
