Motor don"t make thrust, props make thrust. As "Rudeboy" stated, a given prop will create a certain thrust at a certain rpm. What is important, is what rpm will a given engine turn, say a 26x10 "Acme" prop as compared to another engine with the same prop. Now if motor "A" gets it up to 7000, and motor "B" takes it 7500, thats what you want to know. Now a calculator can be used to determine "static" thrust. But , thrust changes as speed increases, & I don't know what the effects of that are.