I recently replaced my impeller in my 1988 Force 125. Since that time I have had no overheat issues but now I can go in forward and reverse gear but cannot throttle up past 3500 RPM. I have checked the plugs and they look good. I noticed that it seems there is a problem with the shift linkage that will not allow me to throttle up fully. The engine manual has been of no use on this. How can I adjust the linkage to allow me to throttle up fully?