OK so we used handgrenades instead of preceision bombing to get to THAT answer...

In summary: If you cook three servos that are all rated for 6 volts, on the exact same throttle set-up...the servo is binding and I really think you should focus on the pushrod assembly.

You wouldn't happen to have the engine soft mounted would you? Or does the engine have excessive vibration and/or motion when it is running? Loose mount?

Tom