What is the voltage on CD4017 outputs?
CD4017 is a CMOS device, and as such, the output high voltage will be essentially the rail voltage when the output is sourcing no current.

The output impedance is essentially resistive for small output currents, and the voltage drop with respect to the rail will be more or less linear with current. The datasheet specifies the minimum output current when you have a drop of 500 mV, at least for rail voltages of 5 V and 10 V.

Although it has graphs of output current versus output voltage drop all the way down to the other rail, these should be regarded as transient figures, useful for seeing how fast a capacitance will be charged by the output, rather than as recommendations for what continuous current can be drawn.

The datasheet will have a graph of voltage drop versus output current.