What are the differences in thses motors?<br /><br />I am considering buying a 1997 Nitro with a 120HP Tracker engine on it.<br /><br />Tracker engines are made specifically for Nitro Boats, by Mercury, but what are the differences in the Trackers and an "actual" Mercury?<br /><br />Are they comparably reliable?<br /><br />Are there concerns I should be aware of when considering this motor?<br /><br />Thanks.