I just removed an old school still working temp pick up thru hull from the Livesay. I drilled the nut on both sides as someone coated the threads with some type of hard sealer. After drilled to break the shoulders on bronze nut it flipped right open with a screw driver allowing me to push the thru hull sender right out. So my question is and I'm leaning towards installing a thru hull mechanical plug if one exists instead of grinding and making a fiberglass patch plug. I could go either way cept the 5/8" hole is clean and might make a good future thru hull transducer location. Anyone have ideas on installing a mechanical thru hull plug ?