Okay, I don't know how much simpler I can make this statement:
A motor with only 50 hours on it is barely used - and likely, it broke down during the warranty period. It's very suspicious to me that this engine was *not* repaired when it was still covered under warranty. The OP made no mention that this engine had been sitting in a crate, or hung on the back of a boat that just sat, unused, for 9 years. It happens, but it doesn't happen that much. I seriously don't understand what is so hard to grasp on that concept, which I've tired clarifying. I'm not illiterate, and I understand this engine is 11 years old. It only takes a handful of trips in a year's time on any water body of any size, to put 50 hours on a main engine. I have a hard time believing someone would let a newer motor just sit there, broken, if it broke under the warranty period - unless the engine was subject to severe abuse, or there's more to the story that the OP isn't telling us. 50 hours on an 11 year old motor sounds terribly fishy. 50 hours is barely broken in. This leads me to believe there is a lot more to the history of this engine than is being let on - and quite possibly there's a lot more wrong than just some gunked up pistons. It could be worth sinking $400 into - but then again, you could easily wind up spending as much as a newer *running* engine getting this one fixed up. If I were going to entertain buying this engine, I'd have to drag along an outboard mechanic to give it a twice over before thinking about pulling out my wallet. The OP only has 14 posts here, in over a year's time. It raises a bit of a red flag.