168. Effect of mortgagor's want of legal estate.

Where a mortgagor purports to mortgage a greater estate in property than that which he possesses, the conveyance1 or transfer2 by which the purported mortgage is created passes to the mortgagee such interest as the mortgagor has in the property3. Thus where joint owners of a property purport to grant a mortgage but it is void or voidable as against one of the joint owners, the execution of the mortgage by the other takes effect as an equitable charge over his beneficial interest in the property