It's a safe bet that the engine I am trying to use has 5 volt electronics. If that's the problem then this really sucks. Most of my MTH fleet is older stock. I can try a more up to date engine and see if the problem goes away.
This is the first time I am hearing about explorer having issues with older mth electronics. I probably would have skipped it if I had understood this to be the case.
Thanks for the info.