Tech, why not do that test.. and I dont know if the props are interchangeable or how to find out. Hopefully you can get an accurate measure of peak speed in ideal conditions with the only variable being the different prop.. I would be interested in knowing this also.
The two props you listed differ by pitch only and are the same diameter. We dont know if the blade area's are the same which is another variable but assume they are.
I will assume the TI and the AI are about the same. My guess is the higher pitch will be slower than what came on the Suzuki. Here is the video I did within the last year trying to make sure that the Suzuki was not exceeding 6000 RPM with the stock prop - I dont think it does. If you put on a higher pitch prop, most likely you will get lower RPM and lower HP out of the outboard.
https://www.youtube.com/watch?v=kNbpoeaCe80 The only reason to go to higher pitch with the Suzuki 2.5 is if it was rev limiting - but that is NOT the case.
That Tohatsu 2.5 displacement is 85 CC compared to the Suzuki 2.5 at 68 CC so is a larger motor (same as the 3.5 hp Tohatsu). Both outboards have the same gear ratio of 2.15 to 1.
The Suzuki gives its wide open rpm as 5250 to 5750 and the Tohatsu 2.5 WOT is 4500 to 5500. Ie, the 2.5 Tohatsu has lower peak rpm.
The larger Tohatsu can deliver the same HP as the Suzuki at lower RPM because of the larger displacement and higher torque. Notice also that the 3.5 hp Tohatsu has nearly identical specs but the WOT rpm is higher at 5000 to 6000.
Remember that HP =torque times rpm.
Anyhow.. I think the higher pitch prop will result in lower rpm on the Susuki than the stock prop so less HP and slower top end speed. If the blades are different area or shape, then we have a new variable and who knows then. More area would have a similar effect as higher pitch
But.. I could be wrong.. give it a try and see what happens..