Ditto. Whether the boat speed is 1.5 knots or 9+ knots under sail makes little matter to me. Whatever the speed, that is what it is. No hurry to get anywhere, because it is all about time on the water.You may find that the prop is the least of your concerns.
Good words of wisdom for any new boat owner!! That is what I was suggesting to in post #5. Given the OP's boat year (2006) it is probably due new sails. In that case think cruising laminate sails if the OP wants more speed while sailing...........Before you rush out to spend money on a folding prop, perhaps it would be wise to protect your boat budget and take this year to learn about your boat. You may find that the prop is the least of your concerns.
The problem with the sailors' perceptions is that they are probably only opinions. I say this because I know how difficult it can be to measure precisely one's speed through the water (STW). I expect most sailors depend on the STW reading of their speed log although this instrument must be calibrated. Even though, one with a calibration error should still report a difference in STW between the two propellers even if absolute values were off.Looking at KG's math using the PHRF time adjustment the 90 seconds translated into units of speed does not show much mathematical advantage to supporting a purchase of a folding prop.
Listening to sailors that have a folding prop they see their race time gain as more significant than the 90 second calculation from PHRF.
The accepted number is 0.5 to 1 knot.