Gonna have to throw the BS flag on this one! That kohler big block is one tough engine, and them hydros dont get hot enough to transfer EXTRA heat to the engine. The engine is AIR COOLED meaning it draws air through the top and forces if between the cooling fins. That engine just like any other engine will fail if it's overheated from what we at the shop would call owner neglegence. I repair and replace kohler, kawasaki, briggs, vanguard. This can happen to any of them and is quite common on engines that have oil leaks or typical maintenance is not performed.