Mercury Repair Questions? Ask a Mechanic for Answers ASAP
well I would assume it is one of two things either a clogged exhaust or a bad ignition control module.
However there is another coolant temp sensor that only sends its information to the computer and it helps control fuel control. If this sensor is bad it could cause this problem but not likely usually it will not let the engine start at all.
First thing i would do is check for spark once the engine will not start. Let me know how that goes and we can go from there.