Have a 1999 Mariah with a Mercrusier 5.0L (2 barl. carb). Replaced Sparkplugs and wires recently. Motor started right up and ran smooth for 20 seconds. Restarted great and died again. Seemed like a fuel problem sense it was running ok. Replaced 2 fuel filters and the electric fuel pump. No change. No check valve coming from fuel tank to the fuel lines so that can not be the problem. I still need to check vent line to see if it is parlty blocked. The way this motor dies at any speed within 20-30 seconds make me think a sensor is shutting off motor. What do you fine folks think?
