I am not sure of the diameter you can put on that engine but , I do think you need to go smaller
there is a reason why you are not reaching full rpm
and you are not getting the boat out of the water enough by the sounds of it, not enough front lift like I said in the other thread..
the only water the boat should be touching is at the very back of the boat...
I have owned 10 bass boats and did tourneys for 12 years, so I am just stating what I learned over the years through trial and error
I would call up Paul at Top Gun Marina outside of Bradford 905-775-0862 and ask him. tell him you want to buy a better used prop for it, he has always let me try props till I get it right