SDK switching by its self

The default SDK that im currently using (9) keeps on switching to SDK 6 every time I start a project. Even when I apply the change next time I reboot intellij the SDK switches and therefore I get these annoying warnings:

• Warning:java: source value 1.6 is obsolete and will be removed in a future release
• Warning:java: target value 1.6 is obsolete and will be removed in a future release
• Warning:java: To suppress warnings about obsolete options, use -Xlint:-options.