Re: Merc 5.7 engine rattling after sitting 1 month
After reading through the post and responses, one thing seems to remain constant: the noise begins and ends at approximately 1900 RPM. Above it - noise; below it - normal. I've worked on more car engines than boat engines, but a GM small block is the same no matter where it is. I've had the experience of having a bad lifter or two on a small block which would "leak down" at higher rpm, opening the gap between lifter, valve, and push rod. When we worked on a car engine, we would use a modified valve cover to control oil splash and would run the engine with a squirt oil can handy to flood a questionable lifter. That's quite on job on the Mercruiser engine because the exhaust manifold has to come off to get the rocker cover off. A mechanic's stethoscope will help you isolate which side of the engine the noise is coming from so you'll, hopefully, have less to disassemble to check it out. Good luck and let us know what you find. Hy
