Your engine may or may not be OK. The low compression you feel may be the result of improper breakin, or it could be from some other source. How it runs is the determining factor.

The RPM measured is very dependent upon the propeller and fuel. We can only state what we use to give a comparison. As soon as the brand of propeller is changes, performance numbers will change, sometimes dramatically.

We've never used a Bolly prop, so we have absolutely no idea how they should perform. In all of our testing, we us APC because they give us very consistent results when we make replacements.

An 11 x 6 APC will turn in the high 12,000's, and a 10 x 7 APC will usually turn in the mid-12,000's. That's using the stock muffler and Omega 10% nitro fuel.

Your engine may be running just fine with the props you're using. Blade profile and thickness can make tremendous differences in the resulting RPM. However, if your engine is performing low, then you may need to replace the piston/cylinder assembly and re-breakin your engine.