I recently bought a 1999 Bayliner Express 2452 in very nice condition. When starting the Mercruiser 5.0 engine every few days and letting it idle I notice the engine starting to get sluggish and eventually stopping and unable to restart. Changed sparkplugs and started first crank but, noticed old plugs were in good condition but were black and sooty. Checked compression: 190/195 PSI all 8 cylinders. Rotor, cap and wiring look to be in good condition. I believe the carburetor is a Mercury 2 barrel. Did fine out on the water with 17" prop at 4400 RPM WOT but something is defiantly wrong it should idle for a long time without loading up. I get minimal stinky exhaust on startup then quickly runs clean. Could this be a carburetor issue or bad valve seals, piston oil rings or ??? Engine has 350 hours on it. Thanks for looking and any advice you want to offer. Dennis