Pete Sounds like you have had similar problems with both engines. I would make sure there is not a problem with the fuel tank and associated fuel lines. Seems like both engines are having a similar problem, so it's time to look at issues that could be affecting both engines. From what you said it doesn't sound like air inlet and outlet is the problem for cooling. If that is true then something else is causing your engines to run hot and quit. How close to the engine is the fuel tank, and could it be mounted much lower than the center line of the engine ? Also is the tank wrapped in foam rubber or could the fuel be foaming due to vibration if it's not. I'd check out the tank real good if it was me.
