Yes, the two halves of the engine case are connected internally.
"If you have problems with tranny oil (in your case soapy water) being sucked through into the crankcase, replace the clutch side crank oil seal AND the o-ring that is hidden inside the first gear that goes on, closest to the center cases (the one that the balancer gear contacts). The crank oil seal seals between the cases and this gear, the o-ring seals between the gear and the crank, equally important. Dont forget the threads on this side of the crank are reverse, righty loosy, lefty tighty."