Warning: Picking a used borescope over a new one cost me 6 hours of rework
Last month I had to choose between buying a new $800 borescope or a used one off Ebay for $200. I went cheap because my budget was shot after buying new torque wrenches. The used one looked fine in the photos but the image quality was garbage when I got it on the hangar floor. Couldn't see a crack in a #4 cylinder on a Lycoming IO-360 until I pulled the jug and found it by hand. That was a six hour job I could have avoided if I just spent the money upfront. Has anyone else burned time trying to save a few bucks on inspection gear?
Wait, you pulled the jug before you actually confirmed the crack was there with the naked eye? That sounds like you skipped a step, not just the borescope. A compression test or even a boroscope from a different angle might have saved you that tear down.
My buddy Chris bought a used borescope for his Bonanza project and missed a scored cylinder wall until the oil analysis came back. @shanec61 is right, trying different angles or a simple leakdown test might have caught that before he spent a weekend pulling the jug.