I have a Mercury 6.2L that I am having some challenges with lately. I have replaced the ignition assembly, plugs, fuel filter wires and IAC on it. It runs really well when it is cold and even for a long while when warm. But after a good hour of running, it will start to drop RPMs. While cruising at 3500 RPM it will drop to 1500 or so every couple minutes. It is very regular on the timing when it drops RPM. It is not occasional when it drops, it is every couple minutes or so. Also when idling it will just flat out die every couple minutes.
I have no idea. Took my mechanic out yesterday with the computer. No codes and everything looks good. He says it looks like someone turned the key off when it dies. We inverted the kill switch to rule that being faulty out. He doesn't have any great ideas about it. After he left yesterday he wanted me to clean all the battery terminals, that didn't help.
Any good ideas here?