I am needing to remove a 1 1/2" Marelon seacock and thruhull. This is the one with the 3 cornered, bolted down flange. It was installed with 5200. There was no possibility of unscrewing the flush threaded thru hull, so it was hole sawed out to some depth (I think up into the seacock body). I have removed the nuts from the fixing bolts, so the only thing holding the seacock to the hull should be the 5200 on the flange. Access isn't completely clear, but OK. Grabbing the tailpiece and pulling as hard as I can does nothing. Nor, so far, trying to drive a wedge under it. I am intending to grind the outside enough to get to the heads of the bolts, and may be able to get them out of their holes. Worst case I might be able to sawsall most of the plastic off and grind the rest, but it will be messy. If anyone doubts the strength or security of one of these types of seacocks I invite you to come try to break or remove it!

Has anyone got the trick of how to remove one of these?