Thruhull problem on a 38 MY

Just acquired this boat that’s been on the hard for 7 years… started the process to rebed the thruhulls and immediately ran into problem… the thruhull for the engines and generators are a flang type with three bolts sticking out… it has what looks like a white plastic backing plate… I remove the raw water strainer and bolts and nothing I did to break the seal or remove the flang and seacock worked… it is stuck on the hull…tried to chisel underneath the bronze and under the backing plate but no movement… what am I doing wrong… what is the secret to removing this type seacock???Please help!!!

There is a liquid product called DeBond which will loosen 5200 and similar adhesives. That may help. You can also try heat, cautiously.

I suppose there's always an angle grinder, but it would be good not to have to go there.

Groco and others offer synthetic backing blocks.
https://www.groco.net/products/valve...backing-blocks

These blocks do offer extra surfaces for 5200 to bond to, making removal more work still after the 3 bolts and the mushroom is loose.

Take a propane or MAP torch to the metal, doesn't take much to soften the caulking.
Don't be scared, but don't burn the boat down either. There's lots of threads about thu hull removal here on SAM's.
For me the DeBond stuff is a waste of time and effort when you're working on something that's not delicate.

Am I misunderstanding? Are you trying to rebed something so well bed it cannot be removed? Problem solved. It's good to go.

you have to unscrew the piece from the bottom of the boat before removing the 3 bolts, if not the valve inside will spin. a little heat from the outside and it will unscrew. they make a tool to fit in the hole and catch on the 2 tits inside the hole or you can use an open end wrench--use the open end in the hole, spin it until it contacts the 2 tits then put a pipe through the box end and unscrew

Heat is your friend. Nothing else will break it free.

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Originally Posted by madhatter1

Am I misunderstanding? Are you trying to rebed something so well bed it cannot be removed? Problem solved. It's good to go.

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Agreed. These are very well made boats. Inspect, but don't go crazy.