When a motor gets hot the oil becomes thinner. The metal parts also expand. If you don’t stop the motor!!!!!!, at some point, there is no oil left between the metal parts. The motor begins to tear itself apart until it locks up. As it did run for a while, it was likely an impeller failure as Waunnaboat suggested. You should start by looking for another power head. Kf-7’s are plentiful and not as pricey as the KG-7’s. Finding a Super Ten that still has 110+ lbs of compression is not impossible but your odds aren’t good. I had had a Kf-7 with 110 + lbs of compression, and another with 90 lbs. While there was only 1 or 2 mph loss at the top end, the motor with 90 lbs. suffered from a significant loss in acceleration. Still the motor was a lot of fun and didn’t cost much. Video link – https://www.youtube.com/watch?v=sm4M0xnXm-I&t=65s
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.