Abstract: A helicopter transportable mud pump made into three stages, each of which is separable from one another. Each pump stage is made into a lightweight sub-assembly which can be lifted by a helicopter into inaccessible locations. The adjacent crankshaft ends of the assembled pump stages are series connected in axially aligned relationship respective to one another by a special coupling and drive means. The coupling means is comprised of two coacting coupling members, each of which have confronting faces connected together in a manner to dispose the adjacent shaft ends of the multi-stage pump 120.degree. out of phase respective to one another. The coupling halves are identical in design so that only one member must be duplicated during fabrication of the device.