Mercury 150 XR6 issues

I have a new to me 2002 mercury XR6 150 on a Procraft 180 combo. I got it at the beginning of the summer and it seemed to run fine. This past weekend was the first time I had more than 2 people on the boat. When I went to take off, it took a while to plane out, and the engine was making a womp noise over and over. It clearly was not operating at full power. Once on plane and above about 3300 RPM it had full power and sounded smooth.

I went out today and tried a new prop with less pitch to see if that helped, and it did not. With just me in the boat it isn't that noticeable because it gets on plane and above 3300 RPM much faster. I took my grandpa for a ride and he notice that when it is making the noise and struggling, the motor is shaking from front to back. Once on plane the shake is gone. I took some videos of it and posted them to youtube. It is kinda hard to see and hear what it is doing, but if you watch them you might get the idea.

Any help would be greatly appreciated, my wife never wanted the boat in the first place, so now that it isnt working right I'm really in the dog house... haha

edit: fixed the links to youtube a couple of posts down