Not sure if I'll need to change or not. Having a problem getting a new engine to put out more than 3500 rpm, when it should WOT 4800. It may be a prop problem, but I won't know for another week as I'm waiting for a new ignition module to arrive and be installed. Where are you located? and what's your bottom line, as I have not shopped them yet, but may have to go smaller prop to get the engine where it needs to be.