My bolens 17hp tractor has the blades always engaged.

If this is a manual pto check and see if the spring is still on the arm with the engaging pulley.this is what pulls the arm back.
Luck

if this is a manual pto check and see if the spring is still on the arm with the engaging pulley.this is what pulls the arm back.
Luck

No spring seen on the arm.

Are the blades suppose to quit when you raise the deck?

Yes - when you raise the deck and place the arm in the stop slot they are supposed to shut off. They are only suppose to engage when you the arm in the engage slot when gear is placed in neutral.

Look under the foot rest on the right side , there's a little brake band there.when you raise the deck its suppose to contact the pulley and stop the deck.NOT RUNNING lower the deck and put a bar on the brake arm and bend it down some ,this should take care of your problem.
Luck

OK. Thank you I will give it a try. Regards.