Some of you may already know this, but it's a good tip in case anybody else has this problem.
We bought a used boat from a dealer recently. The previous owner had installed pedestal seats on the front and rear decks. The front pedestal was stuck in the base very tightly, and you could tell someone had been using tools to try to get it out. I've never dealt with pedestal seats before so I didn't know what was really going on. When the salesman took the boat on the lake with us before we bought it he said it was stuck because the plastic was swollen from the heat of summer and that in the winter time it would contract and the pedestal would come out. Then he said you could take a 3/4" drill bit and drill out the plastic some and it wouldn't stick anymore.
The boat was a good deal and we weren't going to let something like a stuck pedestal keep us from jumping on the deal since the boat wasn't that old and everything else was good plus the boat was already loaded with plenty of accessories. I figured we probably wouldn't want to use the pedestal while catfishing, but we may want to put the seat there with no pedestal, so I wanted to get it out. Even if we weren't going to put the seat there I wanted it out of the way while we were fishing.
I took his advice, but instead of waiting for winter, I used a can of the pressurized air that you use for cleaning electronics. If you turn it upside down it will spray out a very cold liquid, or at least it makes everything it touches cold because it's evaporating so quickly. I believe it's carbon dioxide, but I might be wrong. Anyway, I turned it upside down and sprayed the top of the base very good, and then sprayed the bottom as best I could with limited access. Then I just sprayed the top for a while. It was basically frosting up the top of the plastic piece. It didn't work immediately, but I kept trying to twist the pedestal and after a couple of minutes it started twisting and then it came right out with no tools. After I went to the store to get some hardware to install the new rod holders, I figured it had plenty of time to warm up and expand back out, so I took a 3/4" spade bit and used it to just graze the inside of the plastic piece. It didn't remove much material, but it was just enough. Now it works like it's supposed to.