I have a Fuji 50 that was converted over to ignition before I bought it and it has a vibration around 1/4 to 1/2 throttle. It seems to be smooth at idle and at full throttle but vibrates quite noticeably in that throttle range. Right now I am running it on a test stand before I put it in an airplane because when I bought it, it hadn't been run since being converted so I wanted to make sure it runs fine. I'm using a 20X10 prop.

The engine came with a Mezjlik 20X10 which I'm assuming it was run with and when I first tried to run the engine, I used this prop and the engine vibrated quite a bit more at this throttle range as well as full throttle and later I found out the prop was out of balance. I should have checked the balance before I ran it but I didn't.

If the previous owner ran this out of balance prop, could this have damaged the engine? Otherwise, what could be causing the mid-range vibration?

Thanks.

Shawn