A geothermal wellhead repair unit including a mechanically set packer to isolate the wellhead for removal and repair thereof. The packer is run into the well string using a running tool. The packer is set by placing tension on the mandrel to set the packing elements and the slip assembly. Once the packer is set, the running tool can be disengaged without gear of collapsing the packer and the wellhead removed for repair or replacement. Upon replacement of the wellhead, the running tool can be used to unset and retrieve the packer.