NEVER use a hammer to install or remove a crankshaft, even with a wooden dowel. The hammer blows can cause the ball bearing to bounch hard on the bearing race and "nic" one or the other. To assemble, either press the parts together smoothjly in a vise, or heat the engine, then "overtighten the prop to pull the crank forward. To releave the pressure on the bearings, lightly tap the end of the prop shaft, with a prop tightly bolted on. Place a nut over the end of the prop shaft threads so they are not damaged from the hammer.