Bill,

 

The IO-550G was developed for the Mooney Ovation.  The RPM was reduced to 2500 and 180 hp to "improve reliability".  But the story is the Mooney tail was not adequate to get through the FAA testing at 310 hp.  It's common on the certified side these days to derate engines.

 

The other ES guy at my airport bought a "G" and set the RPM at 2700.  I don't think he even messed with the fuel flows.  I don't think there are any mechanical differences.  That makes it an "N" from what I can tell.  He's been flying on the engine for a couple years now.

 

If you can save some bucks on a "G", I'd do it.

 

Mike Easley

Colorado Springs