I bought a 2013 Nitro Z-7 with a Mercury Pro XS Optimax 150HP 2-stroke. I'm only getting 4900 RPMS WOT fully trimmed up. No jackplate. It has a 23P tempest 3 blade. I did swap the stock Minn Kota Maxxum 70 for a Fortrex 112. I imagine that added some weight, but other than that I can't figure out why my RPMS are so low. I should be getting close to 6000 right? Also on another note any idea the size of this gas tank? Nothing in the manual and online says anywhere from 24-40 gallons so I have no clue.