Inside - one clamp on each 4" exhaust vent, hose was stuck on pretty good, but nothing that a few grunts couldn't take care of.
Outside - 6 screws on the 4" exhaust, and it was adhered to the boat with whatever strong sealant they used in 1988 - it was NOT just silicone, but a hybrid silicone-epoxy type substance. I used a razorblade and a scraper to cut down next to the exhaust ports and crack some of the material. It actually came away from the metal easier than the gelcoat. Took me maybe 45 minutes per exhaust port to separate the through-hulls from the hull. Once I had it sufficiently loosened up, a rubber mallet applied from the inside allowed me to push it out the rest of the way.