[Dakota773]

[attachment=799][attachment=799]I couldn't find the original jig i used, but here's a sketch.  Basically, a piece of plywood with a hole large enough for the thru hull, spacers and a top piece of plywood through which i fed 3-4 "J" bolts that I used to pull out the existing thru hulls.  Also, I inserted the J hooks from inside. Using 3-4 allows even pressure around the thru hull. 
  
As for process, I heated the existing thru hulls and adjacent hull area with a heat gun.  Careful not to overheat it but releasing the 5200 that Tiara used would be impossible without the heat.  The key is heat and even pressure and they will release.  You don’t want to put so much pressure on that the thru hull breaks or you separate the gelcoat or hull. Patience and heat, reheat and they will release. All mine came out without any issues.

Lastly, it's a good idea to epoxy the hull opening after the thru hull is removed and everything is cleaned out.  A little ounce of prevention for possible future water intrusion.  I replaced the Thru hulls with Chrome ones and used 4200 as I figured it was a little more workable.

The pictures are for a jig I built to replace the aft scuppers, same idea. 
 
Hope this helps.  E Mail if you have any other questions.