I’m another guy that has done this sort of thing a lot of times. Unlike the previous guy in post #8, I’m one of the guys who moves the torch around & tries to hear the whole part. That has worked for me. I never tried it his way, so I can’t make a comparison.
My standard MO is this:
First look to see what materials you are dealing with. Most brass alloys expand roughly twice as much as most steel alloys when heated, so if you have a brass prop on a stainless shaft, then heat is your friend. If you have a stainless prop on a bronze shaft, then cold is your friend (think dry ice).
I always apply penetrating oil for at least an hour or two before starting removal. If the unit was in salt water, I will hit it with warm soapy water first, & then get it dry before applying the penetrating oil. Kroil is my favorite if heavy corrosion is not present. If it is rusted up, then I use Bust Rust. Another old favorite is ATF with a bit of acetone mixed in.
Now the prep work is done & it’s time to play ball. Getting tension from a gear puller type gizmo is a great start. Sometimes you get lucky & this does the job by itself. Step 2 is heat or cold, depending on the materials present. When I go to the hammer (step 3) I either hit it from the side or gently hammer on the head of the puller screw that is planted into the center of the shaft. I am not trying to hammer the part free. I am just trying to get the parts to ring. When the parts are under heavy pressure from the puller, the vibration of the ringing is what eventually breaks the taper lock grip. Sometimes it takes a minute or two. If I am 5 minutes into ringing it & the parts haven’t separated, then I soak the parts in dry ice for half an hour, followed by quickly heating the female part with 2 torches so that the female is forced to expand before the heat gets to the male part in the center. I had only one experience where I had to do this twice to get the parts to separate. Every other time, it worked on the first go-round. If it wasn’t such a pain in the neck to get dry ice, I would use this method more often. Dry ice is much colder than regular ice. It works really well. It can also be a little dangerous to handle. Wear gloves & have proper ventilation.
At any point in time in this process, the parts may pop apart, so be prepared. You never know when it's going to happen. & as has already been said, the parts can come apart with a dangerous amount of force.
