There are no guaratees that a boat will crank 80 MPH, though in time you should know what your rig will reach on performance. Try rear tackle on heavy items, that helps. Then measure engine heights, which sounds high as you are turning 6000 Rs. Thus we suspect you need to lower the engine height. On a 2008 with a Merc. 225/250 Pro XS there is a definite sweet spot on engine height that changes with loads, and propeller changes. Get the engine height (see FAQ section) and lets start there.
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