if you're getting a used engine in the mail, you'll probably have to dish out some dough as soon as you get it, chances are the person lied and gave you a bad motor...hopefuly you didn't pay too much for it...

anyways, if it were me I'd go w/ this: http://www3.towerhobbies.com/cgi-bin...&I=LXNHG8&P=ML
O.S. makes some of the most powerful and reliable engines out there...I think this would be the best...