2013 255 freedom cavitation issues

[dmc84dds]

Hello
I purchased a 2013 255 freedom with 2013 f300 Yamaha engine. As i pick up speed suddenly or even gradually in certain rolling conditions my engine revs up quickly and the boat slows down. I'll quickly reduce throttle then very slowly bring it
back up to speed and its running OK but sometimes it cavitates again. Also, a separate issue is port list which i was told was prop torque weight distribution is even, it is level when still, but it seems excessive and requires more than 50% trim tab adjustment to level off. Are these two conditions related? Is the prop an issue? (it came with the boat and is in good repair) My feeling after doing some reading is that the engine may be mounted too high. Can anyone make sense of this?
Thank you
dmc

 

[seasick]

Sounds like a spun prop symptom to me.
The prop could be wrong also. That can cause excessive prop slip.

The sound you hear when the motor revs up and speed drops off can be ventilation not cavitation. What hole of the engine mounted in? Can you tell if the ventilation place remains below the water when on plane.Do the checks with no motor trim and no trim tabs.