Ummm, you do know you START with the trim down then trim up...right?
Have you ever had a boat before? Or used one....regularly? Not a big deal if you haven't, but let us know and we can help you. These types of mistakes can add up.
Anyway, what size prop is on it now? Without trimming properly, it is hard to know what your rpm and speed actually is while under way...
We can start with these questions, then help you from there.