TS 650 project, will not go faster than 5 mph in the water
 

I have a TS 650 that I'm rebuilding as a project, I acquired the ski for free. I took it out on the water for the first time and it will not go faster than 5 mph in the water. When I pulled it, I checked the impeller for any trash and it was clean. I'm assuming the impeller is shot, anyone have any ideas? I just ordered the tool to pull the impeller but was maybe seeing if it could be something else.