[sbw1]

Thanks for your reply.
I have an opportunity to get a couple of 20x24 props at a good price.
I'd rather keep the same diameter as I have now and try 21x23 or 21x22 but I'm reluctant to spend the money not knowing for sure if this will improve performance and engine life.

There really is no such thing as a good price on the wrong props. If you are over propped with the current wheels, those will be the most expensive props you will ever run. The new ones, same thing. This is an issue you have to get right. The suggestion to call CAT for advise is a good one. They have a computer system that will provide you with info on the health of your engines, and their techs can answer your technical questions. Achieving the proper WOT is one key to not destroying your engines by overloading them. CAT can help you with the other important things to do for engine longevity.