I just tried this and my macbook pro now kernel panics when I select normal or recovery. Is there a way to recover the OS X bootloader?
Edit: I was able to get my macbook pro booting again by following this post https://www.******.com/r/hackintosh/comments/4ueiww/how_to_remove_clover_if_you_accidentally/ All that was needed was formatting the EFI partition which ended up only being possible from my linux box, after pulling the drive.
First of all: Thank you for the super fast answer.
I did think of ticking that creepy 'Legacy mode' in the first attempt, but anyway redid it as you recommended. Unfortunately there is no effect...
What i found out: the strange boot mask that is loaded when powering the machine on, seems to be Clover, not MultiBeast.
If anyone knows how to remove that and just natively boot back in OS X, id be glad to hear it.
My understanding is that Clover Bootmanager gets installed in BOOT directory in the EFI System partition and the EFI Platform Firmware remembers that as the BOOT partition to boot from (could be the side-effect of running MultiBeast). You can use the Option key to boot into MacOS and use System Settings -> Startup Disk to select the HDD where you have MacOS. If you run the bless utility you should see that your MacOS partition is what gets blessed. HTH.
Also you can mount the EFI System Partition and delete the EFI/BOOT directory in which case you wont see the EFI Boot option in the Boot Menu. I am not sure if that will have any other side-effects in terms of having the USB 3.0 support for the MacOS.