According to the reviews I could find the OS 200-P is a very smooth engine, I also asked an intelligent question that relates directly to big engine shakes. Keeping them below 8,000 rpm is important. Also you need to get the low speed needle set correctly both for a smooth midrange and for economy.
One more thing, how solid is your test stand, if not very solid you are seeing tortional impulses and not vibration. They are the result of a light weight engine coupled with strong power pulses. A heavier prop will help with this.
Last edited by Hobbsy; 07-30-2018 at 01:59 AM.