While I know the hull is rated for a 200hp motor I found the 1999 Yamaha Saltwater Series II 150 on my 190 Tournament hull to have plenty of power. The boat planed off no problem with 4 adults and 3 kids. It also ran at a top end of 47.1mph turning a Yamaha Stainless Steel 3 blade 19"p prop with 2 adults and 2 kids. When I bought the boat, I had the Yamaha mechanic who did the pre-purchase motor inspection raise the motor up and mount it two holes up which put the A/V plate 1/2" above the bottom of the keel. The previous owner had the motor mounted all the way on the bottom set of holes and only saw about 41mph at best. So, raising the motor really help to increase efficiency and top end.
Here is a video of the the final run. The motor turned 5400 rpm @ 47.1mph at full trim with 45 gallons of fuel, 425 pounds of crew and a 4hp kicker.
http://www.youtube.com/watch?v=Nwebg-TTPMc
Also, while I am a HUGE fan of the E-Tec. If you are going with a 150, I would consider...strongly consider the new
Mercury 150 FourStroke. For just under $10,000 (brand new) you are getting a great motor that is as good as an E-Tec for about $5,000 (at local prices) less than an E-Tec.