The gear ratios were different but I don't recall the numbers. The sharing of gearcases really helped the 500s a lot. The gear ratio in the 500s was lowered to allow both the 650 and the 500 to run the same props. I think the strut was maybe a little deeper as well to accommodate the bigger diameter 650 props. When I sold my E Production boat I kept the Bobby Soles built props and ran them on my 500 in SD with pretty good results.

