Honda GB40 Outboard Motor Manual., Page 34Get this manual
2Fit the bearing water seal and vater seal "0" ring the propeller haft; depress the drive chanInto the lower groove of the bottom case for inserting the propeller shaft(81) 3, After completely inserting the propeller shaft, pull the drive chain for engagement with the sprocketFor insuring that the chain is fully engaged with the sprocket, move the chain up and down determine if the propeller shaft rotates smoothly(Fig82)