I think you'ne started something here Justin. I would like to know for the 2011 115hp Pro XS please. From what I'm lead to belive, it's got Fibre Reeds, different pistons and a slightly stronger gearbox.
I'm sure Bob will chime but I believe the XS has a larger fuel intake system and aslo air intake. I think they have domed pistons. I'm sure Bob will update this.
When i bought mine the differences were the following on a Pro XS
Carbon Fiber reeds
Upgraded ignition system
Different ECU tune
Higher RPM limit
The 3.0l motors also had solid motor mounts in addition to the above.
Im not sure if any of that has changed, im sure Bob will know. In my opinion when i bought mine the extra performance and carbon fiber reeds were worth the ~500 dollars to upgrade.
As Jim B. stated, there are a number of differences between the stock motors and the Pro Xs engines. Porting, ecu calibration, reeds, mounts, compressors, etc. My suggestion is to go the the Merc web-site and check out the specs for each engine. Bottom line is that they are ALL at the top end of the 10% allowable horsepower range to still be "legal". In other words, a badged "200" can be 220 and still be called a 200. :blink: