The 525 that you are thinking about was built by Merc, however it is a totally different engine. It was a 454 with a flat tappet cam, Weiand blower and a carb. The engine that the OP is talking about is a Merc 525 efi with an aftermarket Whipple installed.
As long as a reputable shop installed the Whipple, there is no reason that it won't have a long, healthy life. We have done tons of them that have run for 100's of hours. The key is setting it up correctly. That includes the fuel system, water system, intercooler plumbing, etc. Proper maintenance also comes into play. However, if the owner and his neighbor put it on in his garage with his Craftsman tool set, I might be a little leary.

You could always pull the blower, convert it back to stock, and sell the blower. They are a pretty easy sell.
Eddie