NX750 performancehttp://www.ultimatebass.com/bass-fishing-forum/Smileys/modern/r

[oregonbass]

I have an 05 NX750DC w/ 115 Merc 4 stroke. I have been running 52mph at 6000 wot and have been for the most part satisfied. My big complaint has been that it performs terrible in rough water. I just recently installed a CMC 5 1/2 manual jack plate and changed from a 13.25 x 17 aluminum prop to a 13 x 18 silverado stainless prop after  doing some homework. After adjusting the jack plate my boat was handling like a completely different boat. I can now run on water that has whitecaps at 40 to 45 mph with no problems. In my home waters in Oregon  my hole shot is very good and trimmed out I now run at 55 mph w/ GPS at 5800 wot. I thought I had it nailed and problem solved. I took off to Clear Lake in California week before last and fished for the week ( mighty fine fishing by the way). I was very disappointed in my boats performance.It took several hundred feet to get on a plane and sometimes it took my partner getting up between the consoles to get the bow to come down. After get on plane my boat performed as expected except I lost approx 2 mph. The lake sets between 1300 and 1400 feet in elevation and water temp was in the mid 60's. I was disappointed  to the point I called my dealer to get a quote on a 135  opimax. I took it on the river near my house and ran it some more this past Sunday and I was again happy with its performance. I also emailed CMC to see if there was something I overlooked when mounted the jack plate and they suggested installing transom wedges to increase negative trim to help with planing. I was thinking after Sundays run I may need to just buy another 17 pitch stainless prop to run in those conditions when needed.Although more HP never hurts but it may not be much bang for the buck if you know what I mean. 
Does anyone have any other input or suggestions that may help?   

[E5Zero]

I sold my NX750 this spring and upgraded to a Z-7.  I had the 90hp 2-stroke on mine and ran 48 mph on the GPS.  I just wonder if the 17 to 18 pitch props are too small, I was running a 22p Quicksilver on mine and it came with a 21p aluminum.  Living in the Houston area we don't have to worry about the altitude, just heat and humidity.

[bass1cpr]

  There's a 3% + or - self regulating  fuel adjust in the system. Your motor was probably outside of those peramatures with the altitude change.