You said it has been falling on it's face at wot ever since you have owned the boat. Correct? I had this happen to me right after a total rebuild. The lobe on the cam for the fuel pump wore off in less than 30min of run time after 1hour and 45min. of break in. My motor had the same symptoms you are talking about. I don't know how to tell you to check this maybe mercman can help in checking this.