I have 1994 5.0 liter with a mercruiser alpha one outdrive,with a quadrajet carb. The engine has a low hours but has been sittting a while. The problem with the motor is it will idle good for about a minute at 800 rpm then the engine speeds up to about 2500 and then dies.If you give the engine some gas it will keep running but it is really rough. After about 30 more secounds it will die. The engine also feels very hot to the touch after only a few minutes of running and it appears to be running rich via the large amount of black smoke coming from the exhaust. The problem to me sounded like the carb, so i bought a rebuild kit and installed it. I dont know much about carbs so i had my father talk me through it. I made sure the float was set to the charts spec. then reinstalled it. The same problem was still there. The engine also has a knocking/rattle coming from between the engine and the outdrive which speeds up with the engine rpm. I have rented a compression tester and all the cylinders were good. Any help whould be greatly appreciated.