I couldn't get the transom to work, but I bought a right angle pipe fitting threaded thingy from Lowe's. I screw the threaded end into the spark plug tube and pull it out. When putting a new tube back in, I use the other end to provide an even pushing force around the perimeter of the tube. And the threads hardly do any damage to the tube if you need to re-use it and can't get the transom to work (and I never got it to work)
Like this, although I am not sure which size it was. I took a spark plug tube with me to Lowes until I found the right size:
Shop Mueller Proline 3/4-in Dia 90-Degree Galvanized Street Elbow Fitting at Lowes.com
Steve