Nitro Z-7 Sport Problems

[Rmoore300]

I purchased a 2011 Nitro Z-7 Sport that came with a Mercury 150 XS last July. Due to a serious drought in Texas my first use of the boat was on Table Rock Lake last September. With 5 average people in the boat I was only able to get on plane if I didn't trim the engine at all. Even then if I attempted to go faster than 30 mph the bow begin to porpoise up and down forcing me to have one of the adults sit forward of the windshield to avoid this. Fuel efficiency was terrible and top end speed (listed at 58 mph) was no higher than 40. Since that initial outing a new more aggresive prop was put on which allows me to trip the motor a little but no where near as much as my old nitro (a 1999 Fish & Ski with a Mercury 115). Bass Pro isn't offering any help. I'm wondering if anyone else has experienced this problem and if yes what do I need to do about it? Bass Pro seems to think the motor is mounted properly on the boat but I'm less certain.