Just my .02, I'm sure their are plenty of rebuilt good motors. I just personally always get nervous about buying a motor that has been "gone through". Like Kaz said depending on what he means by that statement. This big bore two strokes are a finicky animal and require a rebuilder who is very particular and knows what he is doing. I would definitely want to know who did the work and talk to them. However, I think Mariners/Mercs are great, specially the 2.5. My Father in law has one(175) and it really runs. Make sure you have it checked out good.

Matt