if you are going to start pitching up the prop you need to be careful!
With the standard pitch youre unlikely to cook anything as the engine will run out of RPM before it runs out of power(boat unloaded), once you start to increace the pitch, this will load the engine up more, and if the fuel screw is wound out too far to achieve enough power to get the RPM the same with the coarser prop then the EGTs will be rising, you could melt your turbo.
you have two choices now you have found the problem,
1 adjust the fuel screw so the black smoke is just visible under acceleration once the boost has started to build and leave it alone.
2 fit an exhaust gas pyrometer and run at below max allowable EGT for the turbo and re pitch the prop accordingly to achieve the max speed at a sensible combination of RPM and EGT. then-when it blows up(which it will, when you least expect it and at the most inconvienent time
fit a yanmar!