This sounds like a bad idea. Why do you think your engines are that dirty that you need you clean them? Do you do regular oil changes every 100 hours? They should be spotless. My oil looks almost good enough to put back in at 125 hours!
I'm confused. OP, the only thing you have stated/asked is whether a product designed to clean the inside of the engine is bad for the engine. I'm not sure I'm following the reason for the question, in the first place.
I'm with Dennis on this one. If you are asking about a product that is for dealer use only, you don't know how to use it and I doubt you're a dealer then. Not sure what your intent is, as your posts are pretty vague. Are you rebuilding a motor? Do you have a running motor and are wanting to run some through it? More info is needed.
Could be wrong but I thought he was investigating using it to clean the engine via shooting into the cylinders (spark plug hole) or something like that.
Might be talking about the fuel shock treatment that is available to dealers.
"Yamaha Internal Engine Cleaner is a dealer-only applied product that is the strongest and most effective way to clean out carbon and other build-up from the inside of your outboard. "