I would have loved to remove the flange but the rear port flange on my XP is part of the bell housing casting so it would take a lot more than three bolts to remove it.I had same problem last week with my M25XP. I had the motor out of the boat and it was still a pain. I tried everything and ended up drilling it out with increasing drill bit sizes. It's soft metal but it is seized tight to the bracket. I think it would be easier if you can unbolt the bracket from the block (3 bolts) and work on it on a bench.