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I assume the figure in your post 21 is from an owner's manual? I won't disagree with the manual although in my experience the recommended mounting height is sometimes too conservative.

I suggested raising the motor because it is one of the few virtually free methods to change/improve boat performance and can be done in only a few minutes with minimum exertion by two people. It is also a method I've used a time or two with good effect.

Perhaps, as Phil suggests, the engine is not running properly. The video should provide some useful information.