Yamaha 300 HPDI won't go over 1200 RPM -HELP!!

[Machetero104]

Here is my problem:
-Yamaha 2004 300 HP HPDI
-Installed in a 24 feet boat
- Motor purchase used.
- Service done last week in a reputed outboard shop. All filters changed. Impeller changed. New sparks plugs.
- Motor start every time without any issues.
- Gas tank was empty when I purchase the boat and fairly clean in my inspection. I put 50 gallon of gas around 2 months ago and added Yamaha Ringfree.
- The gas lines are the original ones.
- Controls are new
- When in the trailer the motor can reach 3500 RPM in forward gear (did not want to push it more to avoid overheating)
- When I put the boat in the water, is not able to pass 1200 RPM. The motor feels more comfortable running at 900 RPM (5-6 MPH).
- From 900 to 1200 RPM is vibration in the boat, like if the boat is laboring hard. I run the boat at 1200 RPM for about 2 miles. No alarms.

I am lost here. I don't know what to do next.Opinions and advice will be highly appreciated.

Thanks

 

[99yam40]

get it hooked up to a computer to see all the info.
fuel pressures, shift, neutral switch, and all of the sensors

If the ECU thinks the motor is in neutral it will kill more cylinders when you raise rpm

 

[Machetero104]

Thanks "99yam40"
I am in the process of moving to run a test in the outboard using YDS.
Let's see what happen with the results.
I have been thinking in the famous "shift position switch", but if this SW is bad, it won't prevent the motor to reach 3000+ when in the trailer?
Or maybe because there is no load it can reach higher RPM even running in 4 cylinders.

 

[99yam40]

no load on motor and it will run high on even 2 cylinders.
YDS will answer the questions

even if fuel pressures stay in spec there are screens in HP pump and injectors that can limit fuel into the cylinders