I recently bought a 2009 TR20X3 that has been repowered with 2016 Mercury Pro XS after returning from a year long military school. The 2016 Pro XS has a Gen II Torquemaster Gearcase. It is rigged with an ATLAS 6 in hydraulic jackplate with a 4 in spacer.
When purchased in Dec 2018, the boat was rigged with a 27P Fury prop. Boat would run 70 mph at 5450 max RPM at the optimized jackplate setting. Any additional increase in jackplate height above optimized height resulted in pushing the nose down and decrease in speed.
Since this time, I have run multiple other props to try to attain recommended optimum RPM range for engine (5800 RPM+). Below is a list of props and outcomes experienced at the optimized jackplate setting. This data was captured in roughly the same boat configuration (weight) and roughly same environmentals within a 2 week period this Summer:
27P Fury: 65.5 MPH, 5450 RPM
26P Fury: 66.5 MPH, 5500 RPM
25P Fury: 64 MPH, 5600 RPM
25P Tempest: 65.5 MPH, 5650 RPM
26P Trophy: 64.5 MPH, 5650 RPM
Bottom line: I can't get to optimum RPM. The engine has been checked out by a certified Mercury maintainer that is the best I've seen in my 20+ years owning bass boats. This leads me to believe I've got a rigging issue.
In addition, the boat runs on the back pad, but seems to run flat (more like a Ranger) compared to the other Triton boats I have owned in the past, to include a 2009 TR19X3 with a 225 Pro XS. It just doesn't lift.
Another interesting characteristic is the boat ran 63.5 MPH down current (3-4 MPH) on Lake Pickwick, but ran 67 MPH into the same current.
Distance between aft edge of running surface (pad) to the front of the nose cone is 28 in (with cavitation plate parallel with pad). Using the Mercury equation, this equates to a 5 in height between the pad and the cavitation plate as a starting point for jackplate height.
I need help from those that have rigged a Gen II Gearcase on older boats. Although my setback is 28 in, is that enough? I may be focused on the wrong problem, so any help or advice is appreciated.