I think with that engine a 18x8 will do what you ask it too. On most of my 40 to 45 engines I will run a 18x8 to get that pull. I ran a 20x8 one time. (prop Not ezy to find) and it did ok but it was just to much swing. but it did work.. I know to be able to test good you need 4 to 5 props and they are about 15 to 20 bucks. Not cheep just to see what prop is best for what you want.

Paul