08-29-2006, 11:45 PM
Trial and error is always how I've propped my boats. Try the 15 first. If you're not within a few hundred rpms of max., then try the 13. Find someone who will let you return the 15 if you end up needing the 13. There's just no "set" formula for propping, but you'll "generally" gain about 3-4 hundred rpms going from a 17 to a 15. I went through 3 before getting it right on my last new boat. Considering your boat is relatively small, I'd guess the 15 would work if you're close now.
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