Got the boat out today to make sure it was going to run correctly, and at first it ran amazingly. We ran in the 50mph range for around 10 minutes so I was convinced all my problems were solved. So, we fished for a couple hours... and mixed in a couple slow runs in the no wake zone out at Oshay. When we were done fishing, we went to run back, and the motor started acting up again. We got on plane, and got up to about 51 mph for a bit and the motor started to struggle and slow down. When I backed out of the throttle, it sped back up only to slow back down. I tried to run it strong a few more times, but the motor seemed like it was struggling for gas after it got over 25 mph. Both tanks had more than 10 gallons of fuel in them. I just changed the fuel and water seperator 2 days ago, and the spark plugs only have a few runs on them. Where do I look next?