If I were interested in finding out how much thrust a particular engine would generate I would look all through RCU and see what size engines produce what thrust at what altitude and with what propeller and then I would go BUY the one that fits my needs best.

Remember, thrust is a subjective parameter affected by propeller type, make, size and other considerations I can't think of, engine type, make , size, fuel, 2 cycle, 4 cycle, gas, glo, etc., etc., etc, altitude, moisture in the atmosphere, temperature and several other things I also can't think of right now.

To calculate a thrust would, at best, only be a temporary solution which would change by the next day. Ok, so you say you want a ball park figure, Look here in RCU and you can get all the ball park figures you want without spending any money or time or wearing out your calculator or computer. These guys have made a lifes ambition out of recording engine thrust numbers so dummies like me don't have to worry about it.