17 minutes ago, tcbass said:

Update:
 

Talked to my friend and he said it started happening again. He said he'd start going at WOT and then about a minute later it'd go from 38mph all the way down to 32mph but usually around 36mph and the RPMS also went down at the same time. This is with no touching of the throttle and the throttle not moving at all. This is with 3 and 4 adults in the boat.

 

What's the problem?

Was the engine height and/or prop pitch been addressed as per the suggestions above?

3 hours ago, tcbass said:

Update:
 

Talked to my friend and he said it started happening again. He said he'd start going at WOT and then about a minute later it'd go from 38mph all the way down to 32mph but usually around 36mph and the RPMS also went down at the same time. This is with no touching of the throttle and the throttle not moving at all. This is with 3 and 4 adults in the boat.

 

What's the problem?

We've told you 3-4 times what to do and what issues to address and you still haven't done it. That's the problem. 

Is the blinker trim fluid low?  Could be the framasams as well.

 

Your friend should take it to a qualified mechanic.