I have to agree with Neil
That sounds like a very small engine for such a large boat, and not even run in yet.
My last one was 23 ft and had a 60HP inboard diesel on a shaft, we cruised at about 12 knots
If you are Happy with your capability and the boats then please be sure that you have done your research. and the fuel is full on departure
IE leave Torquay on the Flood tide to get a push across Lyme Bay, arrive at Portland at slack tide to avoid the famous overfalls at the Portland race area.
Plan a couple of bolt holes in case the weather gets bad [West Bay, Portland, Weymouth], and if necessary turn back to Torquay before getting into difficulty.
Sorry to be so negative, but the sea has to be given respect. The forcast is bad this weekend and I seriously doubt many of us will be going afloat.
If you go be very careful