Trantor has the best idea for a first step. That mot likely will tell you if it's a problem at the engine, or somewhere else.
You don't say which engine and prop you have. Just to throw it out there, what are the max RPM for your engine? Some engines are slow turning and they top out around 1900 or 2000 RPM. If yours is one of those, the answer could be as simple as you are pinning the engine at full throttle.
Another possibility could be engine alignment. I doubt that's it because you would experience symptons even at the lower RPM, but you never know.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.