To specify a different runtime version for a model version, deploy a new version using the same training artifacts that you used initially. The default runtime version set for a model version cannot be changed. You cannot request online predictions from models outside of Cloud ML Engine, so there is no option to override the default runtime version in your request.

Doing so is likely to cause unexpected errors. You should never use a different runtime version than the default for a deployed model. This is to accommodate getting predictions using a model that is not deployed on Cloud ML Engine. You can specify a runtime version to use when you start a batch prediction job.

If you don't specify one explicitly, Cloud ML Engine creates your version using the current default runtime version (typically the most recent stable version). Doing so establishes the model version's default setting.