Two weeks ago on Lake Austin I was enjoying a beautiful morning of mid-week fishing. Enroute to my 2nd hole of the morning I was running up lake and decided to punch it up to WOT (wide open throttle) for around 30 sec and then backed off to mid-throttle. As I backed off I noticed the motor had a an unfamiliar sound to it and the motor wanted to die as I slowed. It was unclear to me want the problem was on the water since the motor would run OK at idle and wasn't knocking. The motor was vibrating more than usual and sounded like it had a dead cyliner. My initial thought was a fouled plug. I slowly made my way to the ramp and came on home. When changing out the spark plugs I did a compression test on each cylinder and noticed that all but one cylinder were within 5% of each other in pressure. One cylinder (#4) had NO compression. I finally got a chance to tear into the motor this weekend and take a look at what was going on. Here are some pics of what I found. My best guess is that this piston failure was caused by pre-detonation (pinging) at WOT. All 3 cylinders showed below avg carbon build up and looked clean otherwise. The pre-detonation at WOT caused the top of the piston to crack and the top side of the piston ring wall to break. Fortunately the cylinder wall did not suffer much damage and should hone out nicely. I'll post up more pics as I rebuild the motor in the coming weeks. Thanks to all who've provided references to good area mechanics. Special thanks to Kevin (Swimbait) and Scott Stagner for their additional referrals. I welcome PMs from those who've rebuilt outboards. I've only worked on car motors.