Shot in the dark.

Tony did you say that you did! break the prop? if so did you replace it with a new prop? and again if so what type of prop did you go back with?

If you had a wooden or an APC composite prop and switched over to a master air screw then you will get a little vibration as the MA's will cause a small bit of vibration.

You will have to try and break the tank loose by any means possible. The tank is entered and exited through the fuse. Maybe using a razor/pocket knife might help. Its best that you check all of the fuel lines and the tank as well.

Other things to look for in the fuel line behind the needle valve feeding the carb, are you seeing air bubbles when you tilt the plane up. This will tell you if you are sucking air. If you are seeing bubbles in the line as it lies flat then you might have a hole in the line.

Again it is also a possibility that the shaft could be bent. If being that the case then I wouldn't worry as that engine is easily replaced at a small cost, you might even option for the OS FX series.

Randy