i just went through this whole process and it was hull!
My keel was so rusted it swelled and would stick at about 40 percent down.
Chipping away at 30yrs of rust until it ripped free of hull was easy part.
Anyways i chose to chip, grind and sand away layers of layers of cancerous rust. I then painted on rust dissolver jelly and let it blacken up.
I then lifted it up on a crane with a rope thru bot hole, and coated the mangled surface with epoxy resin and layers of fiberglass.
After that it was a light sanding and bottom paint.
Getting it back in was a work of art as i did this in my backyard/water
Basically craned the heavy SOB onto a wooden ramp cradle made from pressure treat scraps.
Then moved the boat over keel during high tide and waited until tide recede.
Seeing the bolt hole is below water line (only god knows why?!), attached crane to bow and very carefully, patiently position boat over keel until holes lined up.
Was a total PAIN
Boat is much faster with a smooth keel, but let me tell ya, we have had strong winds her in Boca Ciega Bay and i figured YES! I can finally drop my keel 100% and push this little ship. Well, NO
I find the boat is way WAY faster at half keel. Full keel, even in 15-20 knt winds feels like an anchor overboard?!
Also makes boat feel like it lumbers and in chop the damn thing swings on the line and makes me fearsome of a strong swing ripping the boat apart!
Seems i can never get this boat to sail upwind without the pusher motor
Overall a great design if you want to pull up to any beach, but a sh~t design for ACTUAL sailing
Anyways, DO NOT remove the keel unless it is necessary, absolutely necessary.
Acid wash or rust dissolver and paint if its minor, you may need to glass if it was falling apart like mine.
Check your bolts, holes, cables, etc.
Actually check the whole damn boat especially mast step, rigging, dot dot dot
best of luck