To check the ware of the rings, and the cylinder, remove one ring. Place it in the bottom of the cylinder, below where it runs. Get the ring square in the cylinder. A piston skirt is often used but anything true, that just fits to straighten the ring will do. A machinist rule or caliper will also work. I’m sure you can find a way to get it done. The end gap, when new, should be around .006 to .008 for a 1.5 inch bore. Then move the ring to the top of its travel. That difference in the end gap, from bottom to top, is (roughly) how much taper you have in the cylinder. 3 or 4 thousands should be expected. 10, 11, 12, thousands or more will result in a significant loss of compression.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.
